CHAPTER 1.  continue

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much farther north. Gravel and river deposits cover the southern portion of Falls township.. Near the northern edge of the gravel we find terraces and escarpments. These escarpments have a diagonal course across the township. marginal the successive courses of the Delaware river as it has gradually undermined the newer formations which are now eroded or concealed below the alluvial on the Pennsylvania side, but are visible on the Jersey side of the river. Northwest of Morrisville, in this township, appears a depression in the Potsdam ridge, and in the neighborhood of Rock run, where this stream runs into Lower Makefield township. The Delaware river possibly at one time crossed to the south side of the Potsdam at this point, and worked its way in a northwesterly direction towards Fallington. It appears that the outcrop of the Wealden deposit at Turkey Hill is the only place in the state where this clay is found.
    Crystalline limestone occurs in Southampton township, near the Neshaminy creek. It is interbedded with Laurentian rocks, and occurs near their northern edge. The locality is well known as a mineral district. Plumbago is found interspersed throughout the limestone. The extent of the limestone deposit appears limited and local in character. A hornblende gneiss is ill contact with the limestone both north and south, and even splinters and small blocks of the dark gneiss are involved in the crystalline limestone, as if ruptured from the walls of a fissure through which the carbonate of lime of the quarry and the included minerals may have gushed up. Some of these flakes of gneiss are excessively contorted and folded, indicating the whole mass to have been at one time in a pasty or soft state, and so heated and squeezed as to have softened and folded the included gneiss. The limestone itself is a white crystalline mass, consisting of true granular limestone, granular dolomite, and calespar full of specks of. perfectly and imperfectly crystallized pure graphite, with a variety of other interesting minerals. Orthoclase of a trichinic form has been found in this quarry and analyzed by Professor Genth in 1875. He says in regard to this mineral: 11 It has been stated in my report of 1874, B. 94, that orthoclase occurs at Van Artdalen's quarry, in Bucks county, in cleavable masses ; sometimes opalescent with rich blue colors. I have analyzed one of the latter and obtained highly interesting results. The material for analysis appeared quite uniform throughout, and was of a dark gray color with blue opalescence. The particles showed distinct striation. The analysis gave

              Specific gravity, 2.497.
                                                   Silicie acid........... 64.93
                                                   Alumina .............. 18.58
                                                   Ferric oxide .......... 0.49
                                                   Magnesia .............. 0.12
                                                   Lime...................... 1.77
                                                   Soda .................... 3.04
                                                   Potash ................ 10.44
                                                   Ignition ................. 1.11

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The analysis agreeing nearly with orthoclase, whilst it, shows the- striation of a triclinic feldspar. By the examination of the crystalline structure it is yet to be ascertained whether, this opalescent variety is not. a mixture of orthoclase with either labraclorite or oligoclase, as the apparently pure orthoclase, without striation and perfectly rectangular cleavage, is found at the same locality, or a new feldspar showing the composition of orthoclase with a triclinic form." It would seem as if some of these minerals and masses had been elaborated from -the gneiss caught in and melted up with more or less of the elements of the limestone. In some places the limestone includes large bunches of serpentine, associated with tale and other magnesian minerals. The presence of these naturally suggests a possible origin by segregation from the dolomitic layers of the originally magnesian limestone.
    In George Justice's quarry, situated about two and a half miles above Morrisville, is a seam of coal about an inch thick. The dip of the rock is about five degrees north, twenty degrees west. It is a fine-grained conglomerate of grayish-white quartz, flesh-red feldspar, small scales of mica, and some fragments of chlorite. At the time of our visit here they were preparing to set off an immense blast. The powder did its work well, loosening several hundred tons of fine buildinc, material. Below Newportville, at Flushing, on Dr. Taylor's estate, a magnesium rock occurs which Dr. Genth has found to be enstatite. Its- occurrence is analogous to the limestone of Van Artsdalen's quarry. The dip of the rock is to the southeast, varying from seventy to eighty degrees.
    Southwest of Feasterville, in Southampton township, a coarse granite occurs, and is quarried. This rock has been used for bridge abutments by the railroad company. It varies in color from gray to red. Along the Neshaminy the rock varies from gray, slaty, micaceous quartzite to a hornblendic syenite. 
    Having defined in a general way the southern boundary of the Mesozoic as it exists in Bucks county, it remains now, before closing this part of the chapter, to give a short resume of the Delaware river gravels and clays as they exist along the lower borders of the county.
    "In order to better understand the arrangement of the gravel and clay deposits extending across the southern end of Bucks and Philadelphia counties the present south bank of the Delaware must first be understood.
    "The Delaware river flows in a southeast direction from Easton to a point a short distance below Trenton, where it turns and flows southwest to beyond Philadelphia. This bend is a right angle, and is caused by the river impinging here against the low, hilly outcrop of the Cretaceous formation of New Jersey extending from near the city of New York to the head of Delaware bay at Wilmington in Delaware.
    "The Delaware river has cut into this formation north of Trenton, and, flowing against the barrier formed by the edge of the Cretaceous measures,

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    has worked its way to the ocean along the line of junction, between the Cretaceous and the underlying crystalline rocks.
    The Cretaceous originally extended some distance north of its present outcrop limit, and the river must have. formerly flowed along a line (in general parallel to its present southwest course) some distance north or northwest of its present channel. Thus we have some slight evidence of its flowing diagonally across the southeast corner of Middletown township, in Bucks county following a course defined on the map by the general northernmost occurrence of the yellow and red gravel.
    " The limits of the Trenton gravel define a course which the river may have bad at a comparatively recent date. The small patches (north of the alluvial deposit) called Bryn Mawr gravel by Mr. H. C. Lewis are possibly remnants of the Upper Cretaceous or, perhaps, of the overlying Tertiary measures.
"The mud and fine sand deposited by the river at the present time is found in numerous places along the Delaware. It is principally confined to the marshes and lowlands immediately adjoining the river. It forms a considerable portion of the extreme southern end of Philadelphia between the Del -ware and Schuylkill rivers." (Professor Hall's Report, p. 15, ch. 2 c. 6.)
    The Trenton gravel extends along the Delaware from Yardley, above Trenton, to Darby creek, below Philadelphia. It is usually a coarse gravel. Between Morrisville, opposite Trenton, and vicinity of the Poquessing creek, through the southern edge of Bucks county, there are two, sets of terraces and escarpments visible. The northern escarpment extends along the general course of Jordan Rock run and Mill creek to the neighborhood of Bridgewater. The southern series of escarpments is marked by the general course of the Pennsylvania canal from Morrisville to Bristol. These escarpments mark an earlier course of the river.
    The yellow and red gravel and Philadelphia brick clay forms -a broad- belt extending from the limits of the Trenton gravel northward to the higher ground. Numerous patches mark the limit of the Cretaceous 'as it originally existed. This gravel is composed of the debris of all the geological formations which exist along the course of the Delaware river, as well, no doubt, as: the; debris from the sands and conglomerates of the edge of the Cretaceous (and, perhaps Tertiary) undermined by the river.
    Large angular blocks of sandstone and quartzite are found in many places. The deposit of clay seems to be in many cases interbedded with the gravel. Whether it be derived from the, wash of the Cretaceous beds, or a deposit similar to the glacial clays of the Hudson river, or whether it had its origin from both sources, is still a question. Its age is unquestionably not. remote from the glacial period. The material which forms much of the gravel with which the clay is associated owes its transport glacial agencies. Whether  

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the ice did or did not extend to this latitude, may still be questioned ; but I think there is little question as to the period when the angular blocks were brought south and deposited here with the gravel. Fragments of fossiliferous rocks have been found in various places. They are of unmistakable Oriskany sandstone and Helderberg slate.
    The Iron-bearing clay group is found at Brownsville, this county, and includes all brown hematite (limonite) iron-ore bearing clays, whatever their origin in this section. Those iron-ore deposits which flank the Potsdam sandstone are all of Potsdam age.
    The Bryn Mawr and other four hundred feet A. T. level gravel patches of Bucks and Delaware counties show that there was once a rise of sea level to that height at least. The valleys of the Delaware and Lehigh in Northampton county must have been arms of the sea into which would have been dropped all the material which those rivers brought down from the north ; and if this rise happened after the formation of the moraine, or during the prevalence of the great ice field, these valleys must have become filled up to a high level with glacial clay, in which no doubt would be included large blocks of stone, such as are found in these deposits.
    Having described the Mesozoic new red sandstone and the gneisses, micaceous schists, etc., of the middle and southern end of the county, under their several aspects, the interesting area comprising the northeastern corner of the county next claims attention. This division of Bucks county north of the Mesozoic formation consists of parallel ridges called the South Mountain or Durham Hills. They are a continuation of the Highlands of New York and in New Jersey through eastern Pennsylvania, ending at the Schuylkill river. The contour of these mountains is long and rather narrow, nowhere sharp, and studded with numerous rounded summits seldom reaching the altitude in this section of eight hundred feet above tide level. The side slopes in many instances are quite, steep. The region is thickly covered with second growth timber. The soil is fertile and in a high state of cultivation whatever cleared. Between these mountains lie secluded valleys of rich limestone land, but these valleys are themselves rather hilly and greatly resemble the limestone belts in Northampton, of which they are outlying fragments separated from each other by the gradual erosion of the limestone strata which at one time covered the mountains, and the removal of which has exposed the underlying syenitic beds. The Bougher Hill range of granulite is isolated from the rest of the range by Wolf's ravine which descends in a southerly direction, the divide being only three hundred and ninety feet above tide level. West of this ravine the range is broken into summits, the highest, south of the county line in Durham, being seven hundred and ninety feet above tide level ; the south edge of the ridge, overlooking Springtown with its limestone quarries, being seven hundred and eighty feet above tide level. The water in Durham creek, in the limestone

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valley at Springtown, reaches three hundred and twenty feet. At Leithsville, about twelve miles from the river, this range of hills practically ends. From Bougher Hill gap the river keeps on the same course, south, about three miles, bending slightly west about half a mile below Riegelsville, until it reaches the mouth of Durham creek. These three miles it is cutting, through the Durham and Musconetcong valley limestone strata. At the heading of Durham creek, near Leithsville, is a narrow opening into the Saucon limestone valley. A mile south of Durham furnace, at Monroe, the river makes a gap through the Musconetcong Mountain range, one of the greatest mountain ranges in New Jersey. But, in Pennsylvania, its summit west of the river rises only four hundred and ninety feet (A. T.), becoming five hundred and seventy feet south of Springtown. But some distance west, about two and a half miles south of Leithsville, it again reaches an altitude of nine hundred and eighty feet (A. T.). South of this range the whole county is occupied by the Mesozoic or new red sandstone.
    The foregoing will suffice to place before the reader the main features of this northern belt extending diagonally across the county, composed of ranges of syenitic (granulite) strata arched into anticlinals, and separated from each -other by valleys of limestone strata. The stratification of the limestone rocks of the valleys is visible everywhere, but so broken and crumpled that their structure must be chiefly taken on a topographical basis.
    The stratification of the syenitic gneiss is rarely to be seen outside of the mines and tunnels. The general trend or course of these long straight ranges of mountains is curiously almost exactly alike, varying in the main only a few degrees. On the other hand the summits or crests of the individual ridges and spurs range nearly due east and west. Owing to the general decomposition of the surface rock, the dip is often difficult to determine. A great help, however, may be found by observing the parallel arrangement of the minerals composing the rock. The anticlinal structure of these mountains can only be observed in a few places throughout this section of country; the proof, however, may be adduced by a course of reasoning. No geologist who has given the matter close attention will fail to come to this same conclusion. That the South Mountain ranges throughout northern Bucks county have not only an anticlinal shape, but an anticlinal structure, is evident to any close observer, and-that when they were bent into upward folds they lifted the limestone and other, superimposed strata into folds above them ; but in the lapse of. ages the overlying limestone and other strata or foundations were swept away, leaving the mountains bare, but the intervening valleys still filled with them. The gneiss of the South Mountain range in northern Bucks county differs materially from, the, gneisses of the southern end of the county. It is for the most part a massive rock in thick beds, similar in appearance to feldspathic granite, but distinctly stratified, containing but small amounts of mica and hornblende; it

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is in many places largely charged with magnetite. There are only a few isolated belts of talcose and chlorite slates exposed. There is often a distinct parallelism in its crystalline structure, the feldspar and hornblende occupying alternate layers.
    It is evident that the South Mountain gneisses belong to a different system from those of the lower end of the county, and geologists who are familiar. with the rocks of Canada, and the Adirondacks mountains, pronounce them with confidence to belong to the Laurentian system.
    Professor Rogers, in his Geology of Pennsylvania, describes the structure of the South Mountain belt on the Delaware river as follows: 11 Tracing, in the first place, the southeastern limit of the tract, we find it to coincide pretty accurately along its whole extent from the Delaware to the Schuylkill, with the northwestern margin of the Mesozoic red shale and sandstone rocks, which spread so extensively through Bucks and Montgomery counties, and which here overlap and conceal the group of rocks we are about to describe.
    "At the Delaware river, the boundary in question passes closely to the little village of Monroe, being more exactly marked by a small stream (Rodgers run) which flows at the base of the bills. Taking a course somewhat west of south, the line runs about three-quarters of a mile north of Bursonton (Bursonville), then crossing Durham creek ranges westward to the vicinity of Opp's tavern beyond which it bears to the northwest approaching Leith's tavern about two miles south of Hellertown. From this point the line of division between the two classes of rocks ranges in a direction a little south of west until it meets the south branch of Saucon, about half-a-mile northwest of Cooperstown (Coopersburg), crossing the line not far from the north corner of Montgomery. Along the line traced the gneissic rocks and limestone, No. II., wherever this occurs are overlaid unconformably by the edge of the Mesozoic. I several instances, however, the precise line of junction is difficult to trace, owing to the large amount of debris lodged near the base of the hills. In other places, which will be noticed further on, the overlying rock is not the ordinary red shale and sandstone of the Mesozoic, but a coarse-grained, variegated, calcareous conglomerate, identical in geological situations and aspect with the rock
    Between Bucher's Hill, which is the northeastern boundary of Bucks county, and the Durham iron mountains or the most southern of the gneissic exposures in this section, lies a fertile valley of limestone No. II., skirted in numerous places by exposures of Potsdam sandstone. This belt occupies the valley of Durham creek as far southwest as Springtown, being along the river about two miles in width. The rocks are well exposed at the numerous quarries throughout the belt. Between the furnace and Durham creek they exhibit a regular anticlinal flexure. This is the locality of the well-known Durham cave, remarkable for the many fossil bones which have been discovered in it from time to

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time. It is geologically situated in the limestone No. II. of Rogers. Chas, B. Trego, in his Geography of Pennsylvania, page 196, published in 1834, says in regard to this cavern In this same township there is a remarkable' cave in the limestone rocks, the entrance to which is about one hundred yards from the river. The height of the entrance of the eminence inclosing the cavern is from two hundred to two hundred and fifty feet above the level of the adjoining lands. From the pathway of the entrance to the rock above is upwards of forty feet, but the passage, being partly obstructed by rocks, will not admit more than two or three persons to enter abreast. The interior is lofty and consists of three spacious rooms ; the passage from one to the other is over steep and prominent rocks. The first apartment is entered by a descent of about thirty feet. The floor of the second room is lower than the first; and that of the third is still lower, in the bottom of which i's a spring of excellent water, supposed to communicate with the creek or river. The entire length of the cavern from north to south is about ninety yards. In quarrying limestone a little east of the entrance to this cave an opening was made into another running parallel with it, and which, though not so wide, is of the same length. This abounds with stalactites, and probably communicates with the other."
The above is a correct and graphic picture of the cave as it existed before 1848; but at present the cave, through the devices of man, consists of one grand and spacious level, combining the second and third apartments in one. It is used for holding scientific gatherings, and will seat if space is fully utilized eight hundred to one thousand persons. Queen Esther's drawing-room is still in its natural condition, and is much visited by scientists and others interested in ancient lore. Catherine Montour has frequently been confused with the Indian queen, and it was the former (who is sometimes erroneously called Queen Esther) whom it was intended to honor.
It is well known to historians that this cave was the resort of the aborigines times, numbers of flint arrow-heads, stone hammers, beads, re found in the recesses, of which there were many, some of into the side walls for some distance. Marks of fire were no doubt, they prepared their food. Parts of a human skeleton were found and numerous fossil bones of extinct animals. An interesting with these petrifactions was a heap of cherry-pits or stones, which were by some means or other deposited where the drippings from the limestone rock above fell upon them, retaining their shape and size. As late as 1855 s fossil skeleton of a deer was exhumed out of the solid limestone rock. The animal, no doubt, became fastened in some manner in a side fissure, and by constant dripping of the salts of lime from above, at last became incorporated with the solid limestone.
The gneiss forming the ridge between the Durham and Roger run valleys, about one mile wide. It is merely a spur of the Musconetcong

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mountain, nosing downward. Its structure is that of a double, antielinal, embracing a very shallow synclinal band of Potsdam, well exposed about one quarter of a mile southwest of the Surface mine, east of a branch of Durham creek. The rock here is much weathered, and the dip rather obscure. The Potsdam rocks here lean upon the denuded edges of the syenitic gneiss, dipping in a nearly opposite direction. The rock consists of a dark silicious slate, and altered sand stone ; upon these repose the lower beds of the limestone No. II., conforming in dip and strike with the sandstone.
    On the south flank, or rather at the south base of the Durham hills, lies a narrow outcrop of limestone, consisting of white magnesian limestone, greenish talcose slate, and blue limestone. The limestone is quarried at Schick's, and makes good lime for agricultural purposes. Abutting abruptly against the blue limestone, we find the conglomerate, which terminates the overlying Mesozoic red sandstone. This conglomerate here is a true pudding stone, composed of pebbles of all the adjacent older rocks-gneiss, Potsdam sandstone and slate, and magnesian limestone-imbedded in a paste of red shale. The conglomerate dips northwest, while the limestone dips southeast at varying angles. This interesting spot, according to Professor Rogers, marks one point along the northern shore of the broad red sandstone estuary, skirted by a bold range of bills, with comparatively deep water at their base, where the crust. disturbances which lifted and drained the district shook down a large body of fragmentary matter, to be rolled and imbedded by the waters along their base.
    Just north of Monroe, on the west side of the road, gray and dark-colored hornblendic, pyroxene, feldspathic gneiss is exposed. This exposure is a fine one. Several hundred yards north on the same side of the road, limestone about one hundred yards in width is exposed, wedged in between the gneissic walls. About one hundred feet north of this, on the same side of the road, we find massive gray-banded granitic gneiss forming a prominent bluff. The rock contains pink feldspar and some epidote, the rock dipping about twenty degrees south.
    It may be of interest to the general reader to learn the probable origin of the magnesian limestones which we find so extensively quarried, wherever exposed, within the limits of the county. F. Prime, Jr., in his Report of Progress, Second Geological Survey of Pennsylvania, page 185, says: "The probable origin of the dolomites and dolomitic limestones has been a favorite theme with many geologists and chemists, and, as a natural result, many theories have been offered as to their probable mode of origin.
    "In many cases, however, wide generalizations have been attempted from limited occurrences of such rocks, or from mere laboratory experiments which were based either on insufficient evidence or else on a forgetfulness of the fact that nature often operates in a manner far different from the chemical labora-

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tory, since she has one important element, viz., time, to aid her in her operations, which the chemist lacks.
    "The magnesian limestones of the "great valley vary from compact to semicrystalline ; are of various colors ; contain very few fossils, and these concentrated in a very few localities. The beds nearest the surface are the most honeycombed by the dissolving action of water; when deeper beds are exposed in quarries they give little evidence of such action. Analysis of these rocks shows that they all contain slight traces of carbonate of magnesia, while some of the beds contain a quantity almost sufficient to constitute them true dolomites."
    He then goes on to give the chemical analysis, which is omitted for want of space.
On page 188 he says: "Bischoff was unable to decompose carbonate of lime by carbonate of magnesia, and, therefore, opposed the theory of chemical precipitation of the latter in the form of magnesian limestone. Scheerer professes to have accomplished the reaction, but does not give his process. His artificial dolomite may have been a mechanical mixture.
    "The chemical theory, however, is sustained in some measure by 'natural pseudomorphs of dolomite after calcite, often with a nucleus of unchanged calcite, or with a vacancy left by the total solution of the calcite. As most of these pseudomorphs occur in mineral veins, the agent must have been (probably hot) magnesian waters; and the carb. mag. must have decomposed the carb. lime. Heat and time are factors in such a process.
    "But the chemical infiltration theory of the formation of our magnesian limestone must encounter a great objection in the unequal distribution of the magnesian carbonate through the mass. It should be either equally or progressively distributed. On the contrary, specimens from the same bed vary greatly, and beds in aciual juxtaposition still more. Thin beds of dolomite lie between thick beds of limestone, and thin beds of limestone between thick beds of dolomite. The analogy between this and shale bands in masses of sandstone I , or sand-partings in shale, makes it hard to believe that the limestone and dolomite beds are not mechanical or mud deposits of mixed materials, floated from a distance by currents from different sources and prevailing over each other alternately.
    " Forchhammer imagined that the limestone waters of rivers flowing into the sea,holding magnesian salts, would produce dolomite beds, but when trying the process with boiling water he could only get 12.50 per cent. of magnesian carbonate in the precipitate.
    "Sterry Hunt modified the theory by supposing the river water charged with carbonate of soda, but the fact of alternate magnesian and non-magnesian beds is still in the way.
    " Dr. Hunt imagined solutions of sodium carbonate, poured by rivers into

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a shallow closed sea, holding in'solution 'sulpbate or chloride of magnesium, and then, by the action of heat, in the presence of carbonate of lime, the deposits changed into dolomites ; but the whole mass would necessarily be homogeneous. Alternate beds- would not be possible without a corresponding number of entrances of the waters of an outside ocean.
    "Hardman makes this objection to Hunt's theory, that nearly pure lime-' stone beds lie between highly-~magnesian beds, and shows that a separate precipitation of carbonate of lime would not begin until at least three-fourths of the sea-water had been evaporated, the carb. mag. still remaining in solution and for a considerable time longer ; in fact, not until concentration had proceeded so far as to make animal life impossible.
    "J. P. Lesley, Director of the Geological Survey of the State of Pennsylvania, adds: I The main force of these objections, however, is derived from the vast extent of the deposits, for they spread continuous at the surface, or underground, from Canada to the Gulf of Mexico, and from the Blue Ridge to beyond the Mississippi river. A sea of such extent could hardly have been closed, and must have received great rivers. But during the long SiluroCambrian age great erosions of land surfaces must have taken place, furnishing mechanical sediments, or if the ocean were merely studded with islands, coral reefs would furnish such sedimentsí "
    The iron mines which form so conspicuous an element in the economic geology of the county are principally found north of the Mesozoic. Of these the surface or Mine Hill mine is of the greatest historic interest. This mine is located on the south side of Mine Hill summit, four hundred and ninety feet above tide-level. The deposit of ore lies between the Potsdam sandstone and the gneissic rocks. The ore is columnar, and pitches thirty degrees east and sixty degrees south, and varies in thickness from eighteen to forty feet. The ore is red hematite, slightly magnetic, and presents a mottled appearance from a mixture of quartz. This is the locality where the early Durham furnace of 1727 obtained its ore for the manufacture of charcoal iron. It is a noticeable fact that wherever, in mining, the old works are struck, no rock has been driven through by the miners of a hundred and sixty years ago. This is owing to the fact that the whole mountain, from its northern base to the southern synclinal, including its summit, is covered (where not removed by the early mining operations) from two to eight feet in depth with ore and soil of the best quality, a-ad these early miners confined their operations mainly to these surface deposits. In one instance, however, these ancient miners ran a tunnel into the mountain several hundred yards in length, but only through the surface ore and soil, evading the underlying, gneissic rocks. The whole mountain is composed of ore, interstratified with gneissic rocks.
    About half a mile south of the surface mine near Geisinger's mill is another out-cmp of ore, not working at the present time.' The ore here is of good

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quality, and large quantities have been mined by the Keystone Iron Company, of Northampton county.
    Several hundred yards northwest, at Charles Gruver's, are some old wokings where much or was mined during 1830-6. The ore is red hematite of good quality, but appears to be almost exhausted in the immediate locality, The ore, when the mines were in operation, was shipped to the Crane Iron Company at Catasauqua. Houpt's limonite mine is located on the southern slope of the second spur of the South mountain, on the north side of Durham creek, half-way between the village of Durham and Springtown. The ore is overlaid by mountain debris of from six to ten feet. Considerable ore has been mined here and shipped to Durham furnace.
    Funk's limonite mine, not now working, is located near Funk's mill, on the east side of Durham creek. Large quantities of ore have been mined here by the Durham Iron Company.
    Geisinger's limonite mine is located about one-half mile southwest of Springtown,
Springfield township, near the main road. The mine is not working Along the southern slope of the second spur of the South mountain, several magnetite and limonite mines have been opened and worked to some extent, but owing to the stringency of the iron market these mines are neglected. A new tunnel is located a short distance east of Durham post-office. This tunnel runs into Mine Hill a distance of three-fourths of a mile, in a direction nearly, due south. Large bodies of bluish-gray ore are exposed here.
    Rattlesnake mine is located on the north slope of Rattlesnake mountain near the summit. The mine is opened by several slopes driven on the ore, which undulates and dips south twenty degrees forty east.
    The ore is variable in thickness, in places from ten to fifteen feet in thickness. The main slope is four hundred feet deep, from which three levels are run, The ore is magnetite, magnetic, and in places polaric (loadstone). Hollow tunnel, located on the east side of Rattlesnake mountain, connects with the Rattlesnake series of tunnels. All the ore mined in this mountain is delivered at the entrance of Hollow tunnel. The ore is the same as that developed at the Rattlesnake mine. Tile rock consists of rusty and dark-colored feldspathic gneiss, interspersed with magnetite.
    It would be tedious to enumerate all localities where this mineral has been found, and a glance at their geological position will suffice. The magnetic iron ores in this section are found interstratified with quartz and feldspar (granulite). The magnetite is widely disseminated throughout the rocks, and is found to be present at almost all localities where the older crystalline rocks are exposed. The crystalline rocks are formed principally of quartz and feldspar. In some cases small amounts of dark-colored mica and pyroxene occur through the rock; occasionally mica and magnetite are found together. The magnetite is generally more or less mixed with quartz and feldspar, although occasionally

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portions of the deposits are met with which are quite pure. The magnetite beds are always parallel to the bedding of the rock, and quite variable in thickness. The observed dip of the gneissic rocks is to the southward.
Limonite (hydrated ferric oxide) ore of iron is an important factor throughout this gneissic range of hills. The crystalline form of this mineral is not known. It occurs in fibrous, radiating, stalactic, baytryoidal, and mammillary masses; in concretions, compact and earthy. Its colors are various shades of brown, the surface often of a black lustrous appearance, the massive varieties dull and earthy.
    A very singular dark mottled ore of iron presents itself in Richland township. This ore occurs on the southern slope of a trappean dyke, and protrudes through a fissure in the rock. It is somewhat magnetic, containing crystals of feldspar disseminated through the ore, which gives it the mottled appearance. Only a small excavation filled with water was visible when it was visited. Several tons of ore were lying on the dump, all having the same general appearance. The prospects for a large amount of ore in situ were not very promising.
    The only other instance of mining operations worthy of mention is in New Britain township, where galenite is mined. This mineral forms a vein of considerable size and richness. The mine is located along the North Branch creek about three miles from Doylestown. At this mine the galenite is found in finecubes, with octahedron and dodecahedral planes.
    An assay of the galenite of this mine showed the presence of two-and-a-quarter grains, or not quite ten cents' worth of gold per ton. The specimen of gold extracted from five ounces of galenite from this locality is exhibited in the cabinet of the United States Mint at Philadelphia. Small quantities of zinc-blende occur -with the galenite. Such ores generally contain disseminated
    In Report D3 of Pennsylvania Second Geological Survey, page 229 occurs a short paragraph in regard to this glacial drift. The report says "North of Rattlesnake hill large rounded bowlders of Potsdam quartzite occur along a branch of Guck creek. The deposit has the appearance of a glacial deposit.
    The above paragraph relates to the glacial deposit covering the northern portion of Durham and extending some distance into Springfield township The greatest portion of it is composed of sand and gravel of different degrees of fineness, con se y mixed together. remarkable fact is grave is not derived from the rocks beneath it, but from those at a distance of some miles, lying along the Delaware or in New Jersey. Scattered through this gravel are rounded masses of rock, of a size larger than pebbles, which are called bowlders.
    Along the valley of the Brandywine, a small tributary of Durham creek

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we find this deposit existing on either side, a distance of over a mile ; the stream cutting through the deposit in places to a depth of ten to fifteen feet, the course of the stream being greatly deflected by these barriers. The deposits have a general southwest and northeast trend. Some of the deposits are crescent-shaped and of considerable size; others merely deposits of bowlders in a heterogeneous mass of small area. The materials of which this deposit is composed are essentially the same throughout the whole area covered by it; beds of gravel, sand, and clay interspersed with immense rounded bowlders of Potsdam quartzite and gneiss.
    The deposit in this county is confined to the extreme northeast corner of the county; but in the adjoining county of Northampton we find these deposits more numerous. The materials or rock masses comprising these hills are rounded or water-worn, showing that the rock masses had been subjected to considerable attrition and the action of water. No rock masses or bowlders composed of the rock formations in the immediate vicinity are found in these deposits, excepting such as were placed here by or through the agency of man; these latter are easily detected by noting their position and composition.
    Before going further into details it will be well to notice a few of the rock formations represented here, not found in the vicinity, and their geological position. It may be of use to the general reader to bear in mind that all the materials composing these drift deposits are more or less rounded bowlders, and the larger portion of these now being described were purposely broken apart to get their actual composition and geological position.
    1st. A black or bluish slate, sometimes gray, olive, or yellowish, sometimes containing rounded pebbles. This rock formation is found extendin on the Delaware from Belvidere, New Jersey, to the Water Gap.
    2d. A hard white and gray or reddish greenish silicious sandstone, quite coarse, also containing pebbles. This formation stretches from the Delaware Water Gap to Franklin county in this state.
    3d. A group of sandstone rocks containing dark olive-colored slaty seams or strata. Many specimens of this formation contain fossil, shells, encrinites, trilobites, etc. This formation covers a large portion of Monroe, Pike, and Wayne counties.
    4th. A brownish-red shale and sandstone, with an occasional layer of 'greenish gray interspersed. Found principally in Pike and Wayne counties.
    5th. Is a somewhat porous silicious rock and of a somewhat doubtful horizon. In its general appearance it resembles scoriae, but its color, which in some specimens is a bluish-white and in others deep to pale red, leads to a different conclusion.
    It would be tiresome to the general reader to prolong the description of the various geological formations represented in these ridges. The above may suffice to give a general idea to those who have followed us thus far.
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    The ridges of gravel, Sand, and clay appear to have been carried by a similar action and at the same time as the larger stones. The small stones which are found in the drift are to a great extent similar in character and are probably from the same localities.
    The depth at which these deposits cover the surface varies, accumulating in some places above fifty feet, while in others the rock is reached in one or two feet. The hill deposits generally present their greatest slope to the South.
    The period of the deposit of this material is very far subsequent to that of the underlying limestone rocks, upon which it rests. A long lapse of time must have intervened sufficient to deposit all the limestone and other formations northward in the state.
    The deposit is distinguished from alluvial deposits by its being found where no action, no existing agency could have produced it, by its requiring, if not a different agency, yet a greater intensity of action for its production.
    It differs likewise from the deposits of the tertiary system, for these are found in limited basins, whereas this is scattered over almost all the northern portion of the Durham valley, and on the top of the highest limestone hills. It is also unstratified, and its situation is such that it could not in general have been deposited by water, yet the sand and clay, which form its upper part, must have been deposited in quiet waters. Finally, when the drift was deposited, the climate must have been colder than at present; whereas the reverse may be stated of the tertiary formations.
    Having thus briefly reviewed the evidences of glacial action in the northeastern portion of the county, we will quote Second Geological Survey, Report Z, page 12. Here J. P. Lesley says: "In Chapter XIX. I have appended a Short description of the course of the moraine throuah New Jersey, so carefully studied by Professors Cook and Smock, and published with copious details in the annual report of the state geologist for 1880. For not only do the mountains of Pennsylvania traverse northern New Jersey, and are glaciated in New Jersey when they are not in Pennsylvania, but the New Jersey drift is swept into Pennsylvaria by three considerable streams, which enter the left bank of the Delaware river-the Paulin's kill at Portland, Beaver brook at Belvidere, and the Musconetcong at Riegelsville. The Delaware river gravels in Pennsylvania, therefore, partly owe their origin to the moraine of New Jersey. But as no drift comes down the Schuylkill river, because its water basin is entirely south of the moraine, so no drift enters the Delaware river below Durham because the great Raritan river water basin carries the drainage of drift into Raritan bay." That the range of drift hills crossing the Delaware one mile south of Belvidere represents the southern limit of the great terminal moraine is abundantly proved by the evidences of glacial action everywhere north of this line, and the absence of all such evidences south of it.

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The whole subject of terrene elevations and subsidences is shrouded in mystery, and whether these deposits belong to the glacial epoch, or to the successive variations in the successive sea levels of the globe, is a question that we need not discuss here. But that these deposits differ from those in the river valley in being composed of unstratified material, and of their being otherwise exact imitations of deposits existing north of the line of the great terminal moraine, except so far as area and size are concerned, is beyond successful contradiction.
Returning now to the Delaware at Riegelsville it is found that the town lies upon a terrace of stratified river drift, which both north and south of the town is heaped into ridges whose axes trend south. This drift extends about a mile north and south of the town, forming quite prominent ridges, covered north of the town with bowlders of gneiss containing epidote and hornblende; bowlders composed of Medina and Oneida sandstone, red shale, and in fact of most of the geological formations between No. 111. and No. X. Sandstones, which outcrop between Belvidere and the upper waters of the Delaware river, are represented in. this terrace, north and south of the town. Many of them are finely striated. Limestone underlies the drift.
    A well recently dug at a prominent point on this terrace gives the following drift strata: 1st, Sixteen feet through paving stones; 2d, five feet quicksand and loose gravel; 3d, eighteen feet very coarse gravel and bowlders; 4th, three feet cement gravel (so called on account of its hardness and appearance of being cemented together by yellow hydrated peroxide of iron); 5th, six feet of limestone soil; 6th, twelve feet of limestone and water. The depth of the well is 60 feet.
    A paragraph or two from the prefatory letter of Professor Lesley in Report D3, page 19, may well conclude this review of the geology of Bucks county; "The State Geological Survey, with all its other work on hand, can only indicate in its reports of progress these subjects of future investigations, and mark out in outline the great facts which will be studied in detail by Pennsylvanians when their interest in this branch of science has been aroused. Much can be done by parties of college students in vacations; but the most of the work will be accomplished by intelligent private citizens of the state, each studying the district in which he happens to live, and communicating his observations to some society which publishes proceedings. There should be a society of local investigators, a field club of naturalists in every county in Pennsylvania, which could easily place itself in active correspondence with the American Philosophical Society, or with the Academy of Natural Sciences in Philadelphia, for the publication of their papers, or they might place them at the disposal of a geological bureau at Harrisburg, for publication by the state.
    "Natural science is now too copious and difficult to be managed by isolated seekers after truth ; its devotees must arrange themselves into communicating

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groups The history of England shows how much more knowledge is gained by a multitude of small corresponding societies than by a few metropolitan academies of science. These last are merely headquarters ; the great army of field-workers must be cantoned about everywhere. Pennsylvania might easily have for itself sixty live geological societies localized in its county towns and at its mining centres."

History of Bucks County By J.H. Battle  Table of Contents