habits, generally hiding under stones, on walls, &c., during the day, and during the night hunting their food, which consists of flies, gnats, and other small insects. They do, however, sometimes hunt during even the brightest part of the day. They should be collected during the latter part of the summer and the early autumn, because at that time they are mature. The collector should look for them on the walls, and about the eaves of barns and out-houses, along stone and other fences, beneath stones in dry or even moist gravelly places, under sticks, fence-rails, logs, and the like in dry, grassy groves. In catching them care should be taken not to break their legs, and they should be dropped into a bottle containing very strong whiskey or ordinary alcohol, or spirits of wine. When practicable each species should be preserved separately in homœopathic or other small phials, and an accurate account be kept of the localities in which they may be captured, and any observations on their habits will be especially valuable. After they have been put in spirits, no further care is necessary, except to see that the alcohol does not evaporate and leave them dry. Hoping that you will be able to obtain collections, I remain yours, respectfully, H. C. WOOD, JR., M. D.

Professor HENRY.

[The Institution will be pleased to receive from its correspondents the speci mens asked for by Dr. Wood, to be placed in his hands for investigation. J. H.]

A PLAN OF A RESEARCH UPON THE ATMOSPHERE.

BY PROF. C. M. WEtherill.

WASHINGTON, D. C., July 24, 1865.

DEAR SIR: I beg leave to submit to your consideration the accompanying sketch of a plan for securing the advantages of a research upon the atmosphere in our country, which would be not only new, but fruitful of important practical results. The work upon which I was engaged last winter, viz., the ventilation of the Capitol extension, has impressed me with the necessity of this research, and I hope that it will meet your approval.

I am, very respectfully, your obedient servant,

CHARLES M. WETHERILL.

Prof. JOSEPH HENRY, Secretary Smithsonian Institution.

The need of a research upon the proportion of carbonic acid (and oxygen) in the atmosphere of the United States.

Plants require carbonic acid, animals oxygen, for their existence; hence an accurate determination of these constituents in the atmosphere is of vast importance, and the knowledge gained from such a research is of great value, both from a scientific and a practical point of view. The question has engaged the attention of scientists (in Europe) from the earliest period of modern chemistry, and its discussion has advanced step by step with the improvement of the methods of analysis. Through the labors of Gay Lussac, Humboldt, De Saus sure, Dumas, Boussingault, Lewy, Schlagintweit, and others we are acquainted with

the proportion of oxygen and carbonic acid in the atmosphere, and the influence, upon the quantity of these constituents, of day and night, winter and summer, rain and drought, of storms, and of elevation. These results have been obtained for Europe, with the exception of Lewy's experiments in South America, upon an atmosphere subject to disturbances from the carbonic acid emitted from volcanoes. The natural tendency of a dense population and a sparse vegetation would be to increase the carbonic acid and to diminish the oxygen of the atmosphere; hence, the United States being in this respect different from Europe, it is of importance to know how our atmosphere differs, as to these gases, from the air of the old country. The research has never been made in America for obvious reasons. Beside, the increased knowledge in respect to the nature of the atmosphere which such a research would yield, important practical results would flow from it with regard to ventilation, to the hygiene of cities and of military hospitals, to agriculture and the clearing away of forests, &c.

The examination of the ventilation of the Capitol extension, which has occupied my attention during the past six or seven months, has deeply impressed me with the great importance of experiments upon the atmospheric constituents, and practice in the kind of analyses required has led me to propose to co-operate with the Smithsonian Institution in the accomplishment of such a research.

In this co-operation I will undertake the analysis of specimens of air collected by myself where located, and of such as may be procured by the Institution from different points in the United States, the localities to be settled by the meteorological experience of the Smithsonian Institution. I will bear the expense of analysis myself, in respect to the determination of carbonic acid, and to a less extent of the oxygen. If, however, a large number of oxygen determinations are made, I would be glad if the Institution would furnish me with the apparatus of Regnault, or with some other improved one, in order to multiply the observations.

[The investigation proposed by Dr. Wetherill is one of much interest, and as full confidence is placed in his skill as an analytic chemist, and his consciencious accuracy in the statement of the results of his experiments, the assistance required will be furnished by the Institution as soon as the Dr. is prepared to undertake the research. It is probable, however, that he cannot commence the work immediately, since some time will be required to enable him to become familiar with the duties of his new position as professor of chemistry in the Lehigh University. J. H.]

AN ACCOUNT OF THE CRYOLITE OF GREENLAND.

COMMUNICATED BY MESSRS. LEWIS & SONS.

[Messrs. Lewis & Sons, of Philadelphia, the proprietors of the mine of cryolite described in the following article, have kindly supplied the Institution with a quantity of the mineral for the distribution of specimens to such institutions as may desire to add it to their cabinets. The Institution is also indebted to the same gentlemen for the account here given and a large map which accompanied it. The mineral cryolite derives its name (from zpos, ice) from its property of melting in the flame of a candle. Its composition is Na. Fl. Al.2 Fl.3=× Aluminum 13.0; sodium 32.8; fluorine 54.2.

It is valuable as an ore of aluminum, for when melted with sodium this metal is liberated from its combination with fluorine, the result being aluminum and fluoride of sodium.

Since the high price of sodium restricts the useful applications of aluminu and its alloys, cryolite has lately become important as a source of soda, considerable quantities of which, with alumina as an incidental product, are manufac tured in Pennsylvania from this mineral.]

COPENHAGEN, November 15, 1864.

GENTLEMEN: After staying a year at the cryolite mines, the nature of which I have thus had good opportunity of learning, I can give you the following information about them, as they were at the time of my departure in the antuma of 1864.

The cryolite mines are situated at Trigtut, (or Triktout,) on the south side of Arsut Fjord, in South Greenland, 61° 13' north latitude and 48° 9' west longi tude. The surface of the vein of cryolite was originally covered with a layer of clay, gravel and earth, which loose material is now chiefly removed, there remaining only in the most southern part of the area of cryolite, a part not yet perfectly uncovered. The boundaries of the vein toward the surrounding mountain is everywhere very conspicuous, with the exception of a part of its northwest side.

The vein, the greatest length of which is about 600 feet, breadth about 150 feet, and extent of which can be reckoned at about 53,000 cubic feet, is of two parts, one close to the Fjord, the other to the east, and separated by a rock from 5 to 15 feet high and about 100 feet broad. The western part is washed by a little bay going in from the Fjord along its whole extent; this is now partly filled up, and will in time be perfectly separated from the sea, when the stone breakwater, now under construction, running in west-southwest and eastnortheast direction, straight across the mouth of the bay, at a distance of about 250 feet from the cryolite mine, is finished, and when the whole of the bay inside the breakwater is filled up, which two works will in all probability be finished before the close of 1865. The rock bounding the vein is everywhere on the boundary line itself 10 to 15 feet high from west, and the south boundary rises tolerably quickly in towards land. The surrounding elevation is chafy of granite, crossed in several parts by veins or layers running from northwest to south.

The principal mineral of the vein is, of course, the cryolite, but as constant

accompaniments we find quartz, iron-stone, lead ore, copperas, sulphur, arsenic, tin-stone, (the last two very seldom.) These substances are not evenly distributed through the whole mass, but the cryolite is partly found quite clean and unmixed; while larger and smaller quantities are found containing more or less of the abovementioned minerals.

A strip of the vein only a few feet broad along the south and southwest boundary of the same is conspicuous for its richness in iron-stone and quartz, but especially for lead ore and copperas. The surrounding mountain is also, in certain places, viz., along the southwest boundary strongly impregnated with lead ore, copperas, and varieties of arsenic, tantalite, molybden ore and tin-stone. In the cryolite are found pieces of the surrounding mountain, both of granite and of trap; it is therefore quite certain that the cryolite has come from the interior of the earth by volcanic agency, and that it is newer than the granite and the trap. The melted mass of cryolite has, during its progress through the granite, torn off parts of the latter and enclosed them in itself. The cryolite vein is what is called a block with face towards south and southwest; in the south and southwest boundary of the vein the cryolite can plainly be seen going under the granite, in a very rapid dip, as much as 25°; at one place, however, where the cryolite forms a kind of peninsula running west, the dip seems to be about 0° 12'; the cryolite appearing to continue under the mountain in a horizontal direction. As far as the quality of the produce is concerned, the cryolite vein consists of two different unequal parts, divided by a breakwater 60 feet high and 110 feet long, running northwest and southeast.

I. The part east of the breakwater, whose greatest length and breadth are about 235 and 100 feet, and whose total extent can be reckoned at about 16,000 cubic feet, consists of two parts-a northerly, 7,000 cubic feet in extent, which is totally of perfectly clean white cryolite, without any mixture whatsoever of unclean minerals, with exception of the mass or part on the surface of the angles or separation, which is colored red or yellow by a very thin layer of ochre or clayey iron; this part runs north and east right up to the granite. In the south and west it is surrounded by the second or southerly part, whose extent amounts to about 9,000 cubic feet, containing only impure cryolite, much mixed with quartz.

The north part is almost all mined to a depth of fourteen feet below high-water mark; the eastern part of the same only to a depth of 11 to 12 feet, and on the western corner a pump-shaft descends to a depth of little more than twenty-two feet below high-water mark. The southern part, on the boundary towards north, is worked to a depth of four feet below high-water mark, but it rises gradually towards the south until it is somewhat over high-water mark.

To keep the east mine free from water an engine is used which works four pumps, and has been more than sufficient to keep the working places free from water. The engine is calculated to raise the water from a depth of forty feet below high-water mark; until the whole mine exceeds this depth no greater power will therefore be required. The mine during the winter is of course, filled with snow and ice, and all blasting must, therefore, cease from the months of November to April. In the months from May to October the mine can be worked, except under unusually severe climatic conditions, and I think in this time, with a gang of fifty men, about 5,000 tons of cryolite can be had.

To convey the pieces broken out to the place where they are piled up, the two following means are used:

1. Toward the north on the granite rock before mentioned, which separates the eastern mine from the Fjord, is a horizontal road, running in a north and south direction on a level of one foot above the highest high-water mark, and on this road is laid a tramway running to a spot which has been filled up in the Fjord, in the middle of which is a turn-table and siding. The cryolite can be shipped from here with great ease, generally without the use of barges. At the southern

end of the road called the heading is a crane for hoisting the cryolite from the bottom of the mine to the tramway.

2. In the south side of the eastern mine is built an inclined iron road, leading from the southwest corner of the mine in a west-northwest direction up on to the breakwater, which forms the west boundary of the mine. Here the iron road is continued horizontally in the same direction, west-northwest, for about 100 feet, where, by means of a turn-table, it is connected with a cross line leading north, and with a stone basin built in the Fjord, where at low-water it has to be shipped in barges. At high-water it can be put at once on board the ships. Under the supposition that the dimensions of the mines remain unchanged in depth, the northern part will yield 630 tons of pure cryolite, and the southern part 610 tons of impure cryolite; estimating the weight of one cubic foot cryolite at 180 pounds, and a ton at 2,000 pounds.

II. The western part of the cryolite vein adjoins the breakwater towards the east which has been mentioned several times before; towards the west and south it extends up to the granite; towards the west the boundary is uncertain. The greatest length and breadth of this part, which on the drawing is marked “C,” are respectively 200 and 120 feet; its whole extent can be reckoned at about 20.000 cubic feet, consisting of medium clean cryolite. About a third of this is blasted to a depth of four to five feet under high-water mark; the rest lies level with highest-water mark, with the exception of a small part extending from the southmost corner along the southeast boundary, where the cryolite rises to a height of five and a half to eight feet over high-water mark. In the front towards the west the cryolite is nine to ten feet over highest-water mark. In the extreme southeast corner of the west part a vertical shaft (with a profile twelve feet long and twelve feet wide) is blasted to a depth of about twenty-four feet under highwater mark; at this place the cryolite became better as we went deeper; it was whiter and less mixed with iron ore, sulphurous particles, and lead ore. By driving a network of horizontal galleries, crossing one another in the western part, from the shaft at the commencement, and supporting the passages with pillars, it will probably not be very difficult to procure, with a gang of about fifty men, 2,500 or 3,500 tons in the course of those months in which the open mine cannot be worked.

To keep these mines free from water, an engine with the necessary pumps is used, which, if the water streaming in does not in future increase in the twentyfour feet deep shaft, will be able to keep the mines clear of water to a depth of about forty feet under high-water mark.

Supposing that the length and breadth of this western part will remain unchanged in descending, each foot in depth will yield 2,700 tons of medium cryolite. The following remark should be made: towards the west the vein of cryolite forms a characteristic point or peninsula, (springing into the side stones,) which has been before mentioned. The space between this point and the stream, about 120 feet west, is occupied by a cupola-shaped hill, whose highest point is thirty-seven and a half feet above high-water. In the northeast part of this, several hollows are found, which have hitherto not been carefully examined, but in which traces of cryolite have been found. These holes have probably formerly been filled with cryolite, which has afterwards been removed or conveyed by running water or other means. From this and the nature of the cryolite in the projecting point, where the vein seems to go horizontally in, we have reason to suppose that cryolite can be obtained under the granite in the whole extent of "D." As it probably continues under the mountain with the same, or with slight variations, from the height with which it enters at the point, (or peninsula,) it will be easily worked by going in under the rocks with horizontal passages, in a level not under high-water (by which annoyance from water will be avoided) either from the sea-side or from the north or from the east.