Chapter 9

The object of this invention is to render unnecessary the use in secondary batteries of a porous pot which creates useless resistance to the electric current, and to store in an apparatus of comparatively small weight and bulk considerable electric force. To this end two reticulated or perforated plates of lead of similar proportions are prepared, and their interstices are filled with granules or filaments of lead, by preference chemically pure. These plates are then submitted to pressure, and placed together, with strips of nonconducting material interposed between them, in a suitable vessel containing a bath of acidulated water. The plates being connected with wires from an electric generator are brought for a while under the action of the current, to peroxidize and reduce the whole of the finely divided lead exposed to the acidulated water. The secondary battery is then complete. It will be understood that any number of these pairs of plates may be combined to form a secondary battery, their number being determined by the amount of storage required. The perforated plates of lead may be prepared by drilling, casting, or in other convenient manner, but the apertures, of whatever form, should be placed as closely together as possible, and the finely divided lead to be peroxidized is pressed into the cells or cavities so as to fill their interiors only.

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THE MINERALOGICAL LOCALITIES IN AND AROUND NEW YORK CITY, AND THE MINERALS OCCURRING THEREIN.

By NELSON H. DARTON.

There will be many persons in the city of New York and its suburbs who will not have the time or facilities for leaving town during the summer, to spend a part of their time enjoying the country, but would have sufficient time to take occasional recreation for short periods. I have sought by this paper to show a pleasurable, and at the same time very instructive use for the time of this latter class, and that is in mineralogy. In the surrounding parts of New York are many mineralogical localities, known to no others than a few professional mineralogists, etc., and from which an excellent assortment of minerals may be obtained, which would well grace a cabinet and afford considerable instruction and entertainment to their owner and friends, besides acting as an incentive to a further study of this and the other sciences. These localities which I will discuss are all within an hour's ride from New York, and the expenses inside of a half dollar, and generally very much less. I could detail many other places further off, but will reserve that for another paper.

The course which I will pursue in my explanations I have purposely made very simple, avoiding--or when using, explaining--all technical terms. The apparatus and tests noticed are of the most rudimentary style consistent with that which is necessary to attain the simple purpose of distinguishment, and altogether I have prepared this paper for those having at the present time little or no knowledge or practice in mineralogy, while those having it can be led perhaps by the details of the localities noticed. Another reason why I have written so in detail of this last subject is, because the experiences of most amateur mineralogists are generally so very discouraging in their endeavors to find the minerals, and there is everything in giving a good start to properly fix the interest on the subject. The reason of these discouragements is simple, and generally because they do not know the portion of the locality, say, for instance, a certain township, in which the minerals occur. And if they do succeed in finding this, it is seldom that the portion in which the mineral occurs, which is generally some small inconspicuous vein or fissure, is found; and even in this it is generally difficult to recognize and isolate the mineral from the extraneous matter holding it. As an instance of this I might cite thus: Dana, in his text book on mineralogy, will mention the locality for a certain species, as Bergen Hill--say for this instance, dogtooth calespar. When we consider that Bergen Hill, in the limited sense of the expression, is ten miles long and fully one mile wide, and as the rock outcrops nearly all over it, and it is also covered with quarries, cuttings, etc., it may be seen that this direction is rather indefinite. To the professional mineralogist it is but an index, however, and he may consult the authority it is quoted from--the _American Journal of Science_, etc.--and thus find the part referred to, or by consulting other mineralogists who happen to know. Again, the person having found by inquiry that the part referred to is the Pennsylvania Railroad, and as this is fully a mile long and interspersed with various prominent looking, but veins of a mineral of little value, at any rate not the one in question, they are few who could suppose that it occurred in that. Apparently a vein of it would not be noticed at all from the surrounding rock of gravelly earth, but there it is, and in a vein of chlorite. This is so throughout the long and more or less complete stated lists of mineralogical localities. Thus I will, in describing the mineral, after explaining the conditions under which it occurs, give almost the exact spot where I have found the same mineral myself, and have left sufficiently fine specimens to carry away, and thus no time will be lost in going over fruitless ground, and further, this paper is written up to the date given at its end, insuring a necessary presence of them.

In order that one not familiar with mineral specimens should not carry off from the various localities a variety of worthless stones, etc., which are frequently more or less attractive to an inexperienced eye, the following hints may be salutary.

There are the varieties of three minerals, which are very commonly met with in greater or less abundance in mineralogical trips: they are of calcite, steatite, and quartz. They occur in so many modifications of form, color, and condition that one might speedily form a cabinet of these, if they were taken when met with, and imagine it to be of great value. The first of these is calcite. It occurs as marble, limestone; calcspar, dogtooth spar, nail head spar, stalactites, and a number of other forms, which are only valuable when occurring in perfect crystals or uniquely set upon the rock holding it. The calcspar is extremely abundant at Bergen Hill, where it might be mistaken for many of the other minerals which I describe as occurring there, and even in preference to them, to one's great chagrin upon arriving home and testing it, to find that it is nothing but calcite. In order to avoid this and distinguish this mineral on the field, it should be tested with a single drop of acid, which on coming in contact with it bubbles up or effervesces like soda water, seidlitz powder, etc., while it does not do so with any of the minerals occurring in the same locality. This acid is prepared for use as follows: about twenty drops of muriatic acid are procured from a druggist in a half-ounce bottle, which is then filled up with water and kept tightly corked. It is applied by taking a drop out on a wisp of broom or a small minim dropper, which may be obtained at the druggist's also. I do not say that in every case this mineral should be rejected, because it is frequently very beautiful and worthy of place in a cabinet, but should be kept only under the conditions mentioned further on in this paper, under the head of "Calcite in Weehawken Tunnel."

The next mineral abundant in so many forms is quartz, and is not so readily distinguished as calcite. It is found of every color, shape, etc., possible, and that which is found in any of the localities I am about to describe, with the exception of fine crystals on Staten Island, are of no value and may be rejected, unless answering in detail to the description given under Staten Island. The method of distinguishing the quartz is by its hardness, which is generally so great that it cannot be scratched by the point of a knife, or at least with great difficulty, and a fragment of it will scratch glass readily; thus it is distinguished from the other minerals occurring in the localities discussed in this paper.

The other minerals so common are the varieties of steatite. This is especially so at Bergen Hill and Staten Island. They occur in amorphous masses generally, and may be distinguished by being so soft as to be readily cut by the finger nail. I will detail further upon the soapstone forms in discussing the localities on Staten Island, and the chloritic form under the head of "Weehawken Tunnel." The surest method of avoiding these and recognizing the others by their appearance, which is generally the only guide used by a professional mineralogist, is to copy off the lists of the various minerals I describe, and, by visiting the American Museum of Natural History on any week day except Mondays and Tuesdays, one may see and become familiar with the minerals they are going in quest of, besides others in the cases. This method is much more satisfactory than printed descriptions, and saves the labor of many of the distinguishing manipulations I am about to describe, besides saving the trouble of bringing inferior specimens of the minerals home.

In going forth on a trip one should be provided with a mineralogical hammer, or one answering its purpose, and a cold chisel with which to detach or trim the minerals from adhering rocks, the bottle of acid before referred to, and a three cornered file for testing hardness, as explained further on. As I noticed before, the better plan of distinguishing a mineral is by being familiar with its appearance, but as this is generally impracticable, I will detail the modes used in lieu of this to be applied on bringing the minerals home. These distinguishments depend on difference in specific gravity, hardness, solubility in hot acids, and the action of high heat. I will explain the application of each one separately, commencing with--

_The Specific Gravity_.--In ascertaining the specific gravity the following apparatus is necessary: a small pair of hand scales with a set of weights, from one grain to one ounce. These can be procured from the apparatus maker, the scales for about fifty cents, and the weights for not much over the same amount. The scales are prepared for this work by cutting two small holes in one of the scale pans, near together, with a pointed piece of metal, and tying a piece of silk thread about eight inches long into these. In a loop at the end of this thread the mineral to be examined is suspended. It should be a pure representative of the mineral it is taken from, should weigh about from one hundred grains to an ounce, and be quite dry and free from dirt. If the piece of mineral obtained is very large, this sized portion may be often taken from it without injury; but it will not do to mar the beauty of a mineral to ascertain its specific gravity, and it is generally only applicable when a small piece is at hand. With more weights, however, a piece of a quarter pound weight may be taken if necessary. The mineral is tied into the loop and weighed, the weight being set down in the note book, either in grains or decimal parts of an ounce. Call this result A. It is then weighed in some water held in a vessel containing about a quart, taking care while weighing it that it is entirely immersed, but at the same time does not touch either the sides or bottom. Both weighings should be accurate to a grain. This result we call B. The specific gravity is found by subtracting B from A, and dividing A by the remainder. For instance, if the mineral weighed eight hundred grains when weighed in the air, and in the water six hundred, giving us the equation: 800 / (800 - 600) = sp. gr., or 4, which is the specific gravity of the mineral. If the mineral whose specific gravity is sought is an incrustation on a rock, or a mixture of a number of minerals, or would break to pieces in the water, the specific gravity is by this method of course unattainable, and other data must be used.

_The Comparative Hardness_.--The next characteristic of the mineral to be ascertained is the comparative hardness. In mineralogy there is a scale fixed for comparison, from 1 to 10, 10 being the hardest, the diamond, and Number 1 the soft soapstone. These and the intermediate minerals fixed upon the scale are generally inaccessible to those who may use the contents of this paper, and I will give some more familiar materials for comparison. 8, 9, and 10 are the topaz, sapphire, and diamond respectively, and as these and minerals of similar hardness will probably not be found in any of the localities of which I make mention, we need not become accustomed to them for the present. 7 is of sufficient hardness to scratch glass, and is also not to be cut with the file before mentioned, which is used for these determinations. 6 is of the hardness of ordinary French glass. 5 is about the hardness of horse-shoe or similar iron; 4 of the brown stone (sandstone) of which the fronts of many city buildings, etc., are built; 3 of marble; 2 of alabaster; and 1 as French chalk, or so soft as to be readily cut with the finger nail. The method of using and applying these comparisons is by having the above matters at hand, and compare them by the relative ease with which they can be cut by running the edge of the file over their surface. One will soon become familiar with the scale, and it may of course then be discarded. As it is one of the most important characteristics of some of the minerals, it should be carefully executed, and the result carefully considered. It is of course inapplicable under those conditions with minerals that are in very small crystals or in a fibrous condition.

_Action of Hot Acids_.--This very important test is never, like the above, applicable upon the field, but applied when home is reached. From the body of the mineral as pure and clean as possible a portion is chipped, about the size of a small pea; this is wrapped in a piece of stiff wrapping paper, and after placing it in contact with a solid body, crushed finally by a blow from the hammer. A pinch of the powder so obtained is taken up on the point of a penknife, and transferred into a test tube. Two or more of these should be provided, about six inches long. They may be obtained in the apparatus shop for a trifle. Some hydrochloric, or, as it is generally called, muriatic acid, is poured upon it to the depth of about three quarters of an inch; the tube is then placed in some boiling water heated over a lamp in a tinned or other vessel, and allowed to boil for from ten to fifteen minutes; the tube is then removed and its contents allowed to cool, and then examined. If the powder has all disappeared, we term the mineral "soluble;" if more or less is dissolved, "partly soluble;" if none, "insoluble;" and if the contents of the tube are of a solid transparent mass like jelly, "gelatinous;" while if transparent gelatinous flakes are left, it is so termed. As this method of distinguishment is always applicable, it is very important, and its detail and result should be carefully noticed. Care should be taken that only a small portion of the mineral is used, and also but little acid; the action should be observed, and is frequently a characteristic, in the case with calcspar, which effervesces while dissolving. The acid used is hydrochloric at first, and then, if the mineral cannot he recognized, the same treatment may be repeated using nitric acid. Both of these acids should be at hand and two ounces are generally sufficient.

_Action of Heat_.--This is, perhaps, the most important characteristic, and, when taken with the preceding data, will identify any of the minerals found in any one locality, which I will describe, from each other. The heat is applied to the mineral by means of a candle and blowpipe. A thick wax candle answers well, and an ordinary japanned tin blowpipe, costing twenty cents, will serve the purpose. The substance to be examined is held on a loop of platinum wire about one inch to the left and just below the top of the wick, which is bent toward it. Here it is steadily held, as is shown in Fig. 1, and the flame of the candle bent over upon it, and the heat intensified by blowing a steady and strong current of air across it by means of the blowpipe held in the mouth and supported by the right hand, whose elbow is resting upon the table. The current of air is difficult to keep up by one unaccustomed to the blowpipe, the skill of using which is readily obtained; it consists in breathing through the nostrils, while the air is forced out by pressure on the air held by the inflated cheeks, and not from the lungs. This can be practiced while not using the blow-pipe, and may readily be accomplished by one's keeping his cheeks distended with air and breathing at the same time.

This heat is steadily applied until the splinter of mineral has been kept at a high red heat for a sufficient length of time to convince one of what it may do, as fuse or not, or on the edges. The first two are evident, as when it fuses it runs into a globule; the last, by inspecting it before and after the heating with a magnifying glass; sometimes it froths up when heated, and is then said to "intumesce;" or, if it flies to fragments, "decrepitates." Upon the first it is further heated; but in the latter case, a new splinter of mineral must be broken off from the mass and heated upon the wire very cautiously until quite hot, when it may then be readily heated further without fear of loss. For holding the splinter of mineral, which should well represent the mass and be quite small, is a three-inch length of platinum wire of the thickness of a cambric-needle; this may be bought for about ten cents at the apparatus shop. The ends should be looped, as is shown in Fig. 2, and the mineral placed in the loop.

Sometimes a mineral has to be fused with borax, as I mention further on in my tables. This is done by heating the wire-loop to redness, and plunging it into some borax; what adheres is fused upon it by heating. Some more is accumulated in the same manner, until the loop is filled with a fair-sized globule. A small quantity of the mineral, which had been crushed as for the acid test, is caused to adhere to it while it is molten, and then the heat of the blast directed upon it for some time until either the small fragments of mineral dissolve, or positively refuse to do so. After cooling, the aspect of the globule is noticed as to color, transparency, etc. Care must be taken that too large an amount of the mineral is not taken, a very minute amount being sufficient.

I trust by the use of these distinguishing reactions one will be able to recognize by the tables to be given the name of the mineral in hand, especially as they are from certain parts, where all the minerals occurring therein are known to us; and I have worded the characteristics so that they will serve to isolate from all that possibly could be found in that locality.

The first general locality is Bergen Hill, New Jersey. This comprises the range of bluffs of trap rock commencing at Bergen Point and running up behind Jersey City and Hoboken, etc., to the part opposite about Thirtieth Street, New York, where it comes close to the river, and from there along the river to the north for a long distance, known as the Palisades. It is about a mile wide on an average, and from a few feet to about two hundred feet in height. The mineralogical localities in and upon it are at the following parts, commencing at the south: First Pennsylvania Railroad cuts where the mining operations are just about completed; then the Erie Tunnel, in which the specimens that first made Bergen Hill noted as a mineralogical locality, and whose equals have not since been procured, were found, but which is now inaccessible to the general public. Further north is the Morris and Essex Tunnel, in which many fine specimens were secured, and is also inaccessible; and last, but far from being least, is the Ontario Tunnel at Weehawken; and, as it is the only practicable part besides the Pennsylvania Railroad and a number of surface outcrops which I will mention, I will commence with that.

_The Weehawken Tunnel_--This tunnel is now being cut through the trap-rock for the New York, Ontario, and Western Railroad, and will be completed in a few months, but will, probably, be available as a mineralogical locality for a year to come. It is located about half a mile south of the Weehawken Ferry from Forty-second Street, New York city, and the place where to climb upon the hill to get to the shafts leading to it is made prominent by the large body of light-colored rock on the dump, a few rods north of where the east entrance is to be. The western end is in the village of New Durham, on the New Jersey Northern Railroad, and recognized by the immense earth excavations. A pass is necessary to gain admittance down the shafts, and this can be procured from the office of the company, between the third and fourth shafts to the tunnel, in the grocery and provision store just to the north of the tramway connecting the shafts on the surface. As it will not be necessary to go down in any of the shafts besides the first and second in order to fulfill the objects of this paper, no difficulty need be encountered in procuring the pass if this is stated.

These two shafts are about eight hundred feet apart and one hundred and seventy feet deep. A platform elevator is the mode of access to the tunneled portion below, and a free shower-bath is included in the descent; consequently, a rubber-coat and water tight boots are necessary. A pair of overalls should be worn if one is to engage in any active exploration below; candles should also be provided, as the electric lights, at the face of the headings, give but little light, and remind one very forcibly of a dim flash light with a foliaged tree in front of it. The electric wires for supplying these arrangements run along the north side of the tunnel for those on the east headings, and on the south side for the west. They are excellent things to keep clear of, as they have sufficient current passing through them to knock one down; thus their position can be readily ascertained.