up with great force in the midst of a beautiful grove of trees. The water is as clear as crystal, through which the pebbles at the bottom, some thirty feet, can be distinctly seen. It is quite cold in the warmest weather.

Limestone is the general name applied to all massive varieties of carbonate of lime, that form beds of great extent, or mountains. Calcspar is carbonate of lime in its purest state. It is generally transparent or translucent, the faces of the crystals sometimes very brilliant, but the bases of the hexagonal prism are always opaque. Its color varies, sometimes perfectly colorless, often of a topaz or honey yellow, and sometimes grey or reddish. Exposed to the blowpipe, carbonate of lime does not swell nor fall to powder, but becomes white and caustic-it is then quick-lime; some varieties are phosphorescent when heated, and shine with a pale yellow light. Satinspar consists of fine parallel fibres, either straight or waved, and has a silky lustre; it fills small veins in limestone rock, the fibres laying across the vein. There is a particular kind of limestone containing a large proportion of bitumen, which, when rubbed or scratched by any hard substance, or slightly heated, gives out a strong fetid odor. Chalk is carbonate of lime of an earthy texture. It forms the cliff's along the south-east coast of England, which acquired for that island the name of Albion. Chalk formations are not often met with in the United States, though it probably exists to some extent. Rockmilk resembles chalk, but it is much more tender. It is found in the clefts of mountains, where it is deposited by water containing calcareous particles. Stalactites are sometimes transparent, and have the crystalline structure of calcspar; sometimes they consist of parallel layers of different shades of color. This rock is often employed for vases and slabs, under the names of alabaster and onyx marble. Stalactites are constantly forming in nearly all rich limestone formations of a cavernous structure. In the district of Port Kennedy, a few years ago, an extensive cavern was reached, where the process of the accumulation of stalactitic matter was illustrated. They are produced from the drippings of minute particles of calcareous matter, from water which percolates through the roof or sides of the rocks. When a small quantity of moisture arrives at the inner surface of the roof, before a drop is formed sufficiently large to fall by its own weight, a portion of it evaporates, and a rim-shaped film of solid matter is left adhering to the rock. Every succeeding drop

increases the thickness of this film, until at length a slender tube is formed, which is constantly increased in thickness as well as in length. In general, the interior is quickly filled up, and becomes perfectly solid; but sometimes the stalactites are hollow throughout a great part of their length. At Port Kennedy, where the process of formation had been interrupted while yet in its incipient stages, the stalactites coated the interior rocks with irregular thin fibres, in some cases forming conical arches, with borders of variegated color, and in others forming pyramids on the floor. The cavern was an object of considerable curiosity during the brief period it was open to visitors, and its numerous chambers presented an aggregate area fully equal to many of our largest public buildings. A concert was held in one of its largest saloons, on the fourth of July, 1846, at which several hundred persons were present.

The limestone formations of this State, at numerous points, afford several varieties of superior marble. The eastern portion of the state, drained by the Schuylkill, is particularly rich in this valuable mineral, and finds a cheap and easy outlet to market. Much of the marble used for building purposes, as well as for monuments and articles of furniture, is obtained within a range of from ten to twentyfive miles around Philadelphia. The extensive buildings comprising the Girard College, were in part constructed from marble obtained in this neighborhood. There are several productive quarries in Lancaster and other counties; but those of Chester and Montgomery are the most extensive and abundant. Some of these quarries are over one hundred and fifty feet in depth, and powerful levers are used to hoist the massive pieces from their beds. At Conshehocken there is an extensive marble mill, where the rough pieces are sawed into patterns to suit the demands of the market. It is worthy of remark, that the edges of our limestone basins usually afford a marble of conglomerated character, beautifully variegated in color, similar to a variety of the Potomac marble, or to that constituting the interior pillars of the House of Representatives at Washington. This marble is a sedimentary deposit, the various pebbles being cemented together by the calcareous matter of which it is composed. Though extremely hard, it is, in some places, susceptible of the finest polish, and the reflection of the atoms upon the polished surface, at first glance, gives the impression of roughness, which is only dispelled by rubbing your hand upon it. A fine deposit of this peculiar rock lies

near Bainbridge, in Lancaster county; also near Reading, in Berks county, while it is elsewhere met with along the borders of our limestone beds, in the vicinity of slate and shale.

This extensive region of limestone, which occupies, in numerous distinct belts or basins, a large portion of the area of what is termed the Atlantic slope is also associated with several useful metals, as the ores of copper, iron, lead, chrome, &c. The region of copper is principally north of the Mine Ridge-(the first chain of elevation met with proceeding in a north-west course,) and outcrops at various points in Pennsylvania, between New Jersey and Maryland, which States it also penetrates. The most extensive deposit is probably in Adams county, where ample preparations for mining have recently been made, in the immediate vicinity of Gettysburg. Mining explorations were also conducted, until lately, in the vicinity of Pottstown, but the ore was not found to be sufficiently productive to justify the continuation of the enterprize. More recently, operations have been commenced near Valley Forge, and the probability is, that they will prove successful. In various other points attention has been directed to this vast mineral formation, and the time is evidently not far distant, when the eastern portion of Pennsylvania will be as noted for its mines of copper and lead, as other parts of the State now are for their inexhaustible and extraordinary deposits of coal and iron.

Native Copper.-Like most of the native metals, it crystallizes in the octahedral system; but perfect crystals are seldom met with. It occurs sometimes in very large masses, but most frequently in branching and leaf-like forms, scattered among the veinstone, or penetrating it; and the surface of these ramifications is often thinly coated with green carbonate of copper, or tarnished with a brown color. In general it is very nearly pure copper, and has the color, hardness, and malleability of the refined metal, as we are accustomed to see it—sometimes it contains a minute proportion of silver.-(Varley's Mineralogy) Lake Superior is the most extensive region in the world for the production of native copper. In some parts of that region, the copper is penetrated by threads of pure silver, and grains of the same metal are scattered through it—à circumstance which has never been observed elsewhere. Its softness and ready solubility in every kind of acid, and in ammonia, distinguish copper from the few metallic minerals which at all resemble it. Copper is one of the metals that has been known and worked from the earliest period;-alloyed with tin, its hardness is much inoreased; and this alloy proved the various kinds of bronze of which armor,

weapons, knives, and other tools were manufactured by the former inhabitants of both the old and the new continent. Axes and knives from the tombs of the ancient Peruvians and Mexicans, chisels found in the quarries of Egypt, and Roman and Gaulish swords of great antiquity, have been analyzed, an i found to contain from 75 to 96 per cent. of copper alloyed with tin.-(Ib.) In the mines of Lake Superior tools and implements, and marks of previous workings, have been found, which can only be attributed to a race far anterior to the present era of the human family. The mines of New Jersey were worked by the first settlers long anterior to the Revolution.

Ruby Copper.-(Red Oxyde of Copper.)-This substance is of a fine crimson color, sometimes almost black, with vitreous lustre, ranging from semi-transparent to nearly opaque. It is brittle, and about as hard as fluorspar, with a specific gravity of 5.6. It is often intermixed with native copper, but seldom with the other ores of this metal. Tile ore is a variety which is intermixed with oxyde of iron and other impurities, and forms thin flattish masses, something like dark colored tiles.

Black Oxyde of Copper-which is more oxydated than the preceding species, occurs in the form of a fine black powder, or in small masses of an earthy tex- ▾ ture, with some other copper ores. Both this and ruby copper are easily reduced on charcoal to metallic copper.

Sulphurets of Copper.-There are several combinations of sulphur with copper, some of which are valuable ores. Copper Glance-or vitreous copper ore-has a dark steel, gray color, and when freshly broken, a perfectly metallic lustre; but the exterior is often black and dull. It is most generally found in masses without any regular form, or filling small veins. This is the richest of all the sulphurets of copper, affording 75 per cent. of metal, and being in general very free from any other. It has been met with in some of the Cornish copper mines, but only in small quantity-but in the Ural mountains it is an object of extensive exploitation, occurring there in nodules of various sizes, disseminated in veins of clay and gravel.

Variegated Copper Ore.-This was long considered to be the same substance as copper pyrites, of which the surface was tarnished; but it differs from it in containing less iron and sulphur, affording about 60 per cent. of copper, while copper pyrites does not yield more than 33 or 34. It is softer than the latter, and the color much redder-and it is less easily fusible than copper glance.

Copper Pyrites.(Yellow Copper Ore)—is the most abundant of the English copper mines. Its color is that of brass, and its lustre perfectly metallic and shining, particularly when fresh broken. It is easily scratched by a knife; differing, in this character, from iron pyrites, which is much harder. Groups of small crystals often sprinkled over other substances, as quartz, calespar, fluorspar, galena, and blende. When pure, copper pyrites consist of sulphur 35.87, copper 34:40, and iron 30-47. Copper pyrites form veins in granite,

slate, and other rocks, sometimes filling them entirely, sometimes distributed in irregular masses varying in size, and occasionally weighing some hundreds of pounds.

Gray Copper Ore.-The composition of this ore varies exceedingly in different localities; but it still presents nearly the same appearance-a light gray metallic substance. It consists principally of sulphuret of copper, antimony, and iron, with arsenic, zinc, or silver, and sometimes with all these metals--the proportion of the latter, in some instances, amounts to seventeen per cent., when the ore is worked for the sake of the silver as well as the copper.

In the same region traversed by the limestone,-(or rather in the valley above the Mine Ridge-) lead is found outcropping at different points. The ores are of various kinds, and in some cases comprise galena, with a plentiful mixture of silver. Extensive mining operations have lately been commenced in the vicinity of Phoenixville, Valley Forge, and Perkiomen; while the veins of the basin have been traced, here and there, over portions of the counties of Bucks, Montgomery, Chester, and Lancaster. The ore is, for the most part, pyromorphite (phosphate of lead) a beautiful mineral, but not very abundant at any one district, though it appears to be plenty here. Its color rises from bright grass-green to yellow, orange, brown, and sometimes a dull violet. Most specimens contain nine or ten per cent. of the chlouret of lead-sometimes arseniate, and those of an orange color, chromate of lead. The chromates are found in great abundance in the Mine Ridge, in Lancaster county, of which we shall hereafter take occasion to speak. The ores are found in other spots in various stages of combination with other substances. In Bucks county, plumbago has long been mined to a considerable extent, and there is every reason to suppose that this interesting mineral, like the others, occupies a large portion of the peculiar formation in which it is found.

Native Lead is of rare occurrence. It has been observed in small grains and laminæ in some volcanic products, and, also, in some specimens of galena. It may be distinguished by its softness and sectility from the galena, which is hard and brittle. Minium (red oxyde of lead) is a red substance, occuring in the form of powder in some veins of galena and calamine. It is the same substance as the red lead used in painting; but for this and other purposes it is prepared artificially.

Yellow Oxyde of lead, which is less oxydized than the preceding ore, occurs