this Vattemare who has troubled them so much, tell them that your dear and beautiful country is ever the object of his sincere devotion, and the subject of his most sacred thoughts.

Believe in the sentiments of respect and thanks with which I am, your servant and friend, ALEXANDRE VATTEMARE.

To Dr. LINN, Senator of the United States.

Copy of the letter of Mr. Dufresnoy.

ROYAL SCHOOL OF MINES, PARIS, September 18, 1841.

SIR: The specimen of oxide of iron, taken from the mountains of Missouri, which Senator Linn, at your request, has sent to the School of Mines, arrived a few days since at Havre, and has already become the ornament of our collections. In the name of the council of the school, I thank you for this magnificent specimen. Notwithstanding its almost gigantic dimensions, (sixty-six millimetres in diameter,) it is complete in all its parts. From a careful examination of it, we are led to believe that the mountains of Missouri contain masses of iron which will compete with the most beautiful mines of Danimoura, in Sweden, which furnish the iron most esteemed in Europe. Besides its interest in a mineralogical point of view, the present of Mr. Linn is highly esteemed by us, because it commences the system of exchange which you have sought to establish between all the nations of the New and the Old Continents, and which alone can secure the completion of our collections. Be assured, sir, that the professors of the School of Mines take great interest in the success of your enterprise, so useful to science, and will concur in it by transmitting to you specimens of mineralogy and geology, for the foreign museums that may wish to enter the field which you have opened with so much devotion..

Even before we were apprised of the kind intentions of Mr. Linn, the School of Mines had delivered to Mr. D. B. Warden, former Consul General of the United States at Paris, and correspondent of the Academy of Science, at his request, a box of specimens of mineralogy, to be deposited in the cabinet of the National Institution at Washington. The School of Mines will not, however, confine itself to their first transmission of specimens; and it hopes that, through your care, the exchanges will become more frequent.

Be pleased, sir, to accept the assurances of my most distinguished consideration. (Signed) DUFRESNOY.

Mons. ALEXANDRE VATTEmare.

From Dr. E. Foreman, of Baltimore: Communicating a paper on the subject of exchanges of conchological specimens.

From Rev. R. R. Gurley, Washington: Suggesting to the National Institution the advantage of purchasing the Indian Museum of the late Colonel Hook, U. S. Army.

From T. Purrington, Washington.

From W. Darlington, M. D., West-Chester, Pennsylvania.

From A. H. Palmer, New-York.

From J. Coppinger, New-York.

From W. Bacon Stevens, M. D., Savannah, Georgia.
From Hon. J. R. Ingersoll, Member of Congress.
From Captain J. Sanders, Engineer Corps, New-York.
From J. H. B. Latrobe, Baltimore.

From Dr. Samuel G. Morton, Philadelphia.

From Joshua Leavitt, New-York.

From S. F. B. Morse, New-York.

From James Glenn, Pratt's Hollow, New-York.
From H. H. Sylvester, Washington.

From Hon. Albert Gallatin, New-York.
From Dr. Marcus C. Buck, U. S. Army.

From W. Harvey Kenney, M. D., Philadelphia.
From Edmund F. Brown, Washington.

From Jared Sparks, Cambridge, Massachusetts.

From Mrs. Dr. James Mitchell, Sidney, New South Wales.
From M. Jomard, Paris.

From Camille Zeringue, Jefferson Parish, Louisiana.

From R. C. Taylor, Philadelphia.

From T. A. Conrad, Philadelphia.

The following letter from the Hon. H. S. Legaré, Attorney General of the United States, was read:

OFFICE OF THE ATTORNEY GENERAL, December 18, 1841.

GENTLEMEN: I have had the honor to receive your letter of the 1st instant, in which you inform me, on behalf of the National Institution for the Promotion of Science, that its constitution makes the Heads of Departments, at Washington, directors of it, provided they consent to serve.

Feeling, as I do, a lively interest in the promotion of all liberal studies, I shall be too happy to contribute, in however slight a degree, to further the objects of your society. But in accepting, as I do, very gratefully, the honor to which I have been officially called by you, I must bespeak for myself the indulgence which I know I shall require, if the active performance of my duties, as a Director, be prevented by engrossing business of a different kind.

I have the honor to be, with high consideration, gentlemen, your obliged and obedient servant, H. S. LEGARE.

Messrs. J. J. ABERT,

A. O. DAYTON,

FRANCIS MARKOE, JR.

The Treasurer submitted his Second Annual Report of the fiscal affairs of the Institution, accompanied by statements giving a detail of the receipts and disbursements during the year ending on the 31st December, 1841; and a list of the members of the Institution, and the payments made by them respectively.

On motion of Lieut. Gilliss, it was

Resolved, That the letter of Professor J. Henshaw Belcher, with the accompanying memorial, be referred to the Department of Astronomy, &c., with directions to report at the earliest expedient meeting of the Institution.

On motion of Mr. Lawrence, it was

Resolved, That the annual meeting for the election of Officers be held on the 24th instant.

Annual Meeting, January 24, 1842.

Present, forty-two Members.

PETER FORCE, Vice-President, in the Chair.

The following Officers of the National Institution were duly elected for the year 1842.

No. 2.

President.

Hon. JOEL R. POINSETT.

Vice-President.

PETER FORCE.

Directors on the Part of the Institution.

Hon. WILLIAM C. PRESTON, U. S. Senate.
Hon. LEVI WOODBURY, U. S. Senate.

Com. LEWIS WARRINGTON,

Col. J. J. ABERT,

Col. J. G. TOTTEN,

AARON O. DAYTON.

10

Corresponding Secretary.

FRANCIS MARKOE, Jr.

Recording Secretary.

GARRET R. BARRY.

Treasurer.

WILLIAM J. STONE.

The Corresponding Secretary announced the arrival of Mr. Castelnau's entomological collection.

Whereupon, it was

Resolved, That a committee be appointed to open and examine the collection, and to report upon it previous to its being deposited in the Cabinet of the National Institution; and, that a copy of the report, giving the number and contents of the cases, and the condition in which they may be found, be furnished to Mr. Castelnau's attorney.

Mr. Jarnes P. Espy, of Philadelphia, exhibited his nephelescope, and briefly explained its powers and uses, and gave an outline of the elements of his theory or philosophy of storms.

The nephelescope of Mr. Espy is a glass vessel, containing about a gallon, fur. nished with a condensing pump and barometer gauge, with an attached scale. With the condensing pump, air could be forced into the vessel, and with the gauge, the quantity forced in could be measured. A stop-cock was also attached to the instru. ment, which, on being opened, would let the air which had been forced in escape. At the moment of escape, there would be an expansion, and the chief object of the instrument is to measure the exact degree of cold produced by any expansion, whether the air employed is dry, or whether it is saturated with aqueous vapor. This, he stated, it was most important to know, from its connection with meteorology; and it was from the result obtained that he was enabled to frame his theory of storms, and other atmospheric phenomena. Mr. Espy stated that he had performed many hundred experiments with this instrument, employing sometimes dry and sometimes moist air; and he found that when moist air was used at the temperature of about 71° of Fahr. the reduction of temperature for a given expansion was only about half as great as in dry air. If the temperature was lower, more than half; and if the temperature was higher, less than half; and in general the higher the temperature the less was the reduction in moist air, and the greater the reduction in dry air. In this way Mr. Espy was enabled to measure with great accuracy the expansion which the evolution of latent caloric during the formation of cloud produces on the air in which the cloud is formed. This expansion he had found to be about eight thousand cubic feet for every cubic foot of water generated in a cloud by the

condensation of vapor. Mr. Espy showed, that a dense cloud is actually produced in the nephelescope at the moment of expansion when moist air is used, and that the quantity of expansion thus obtained by experiment actually agrees with the result obtained by calculation founded on the well known laws of latent caloric of steam, specific caloric of atmospheric air, and expansion of air by heat.

Mr. Espy then gave a brief outline of the elements of his theory or philosophy of storms, nearly in the following words:

Up-moving currents of air may be formed either by heat or moisture. In ascending they will come under less pressure and expand; in expanding they will become colder about one degree and a quarter for every hundred yards of ascent; and as the dew-point sinks by this expansion about one quarter of a degree, cloud will begin to form in the up-moving current, at about as many hundred yards high as the dew. point at the time is below the temperature of the air in degrees.

When the vapor begins to condense into cloud, the latent caloric will begin to be evolved, and the higher the column ascends the more vapor will be condensed, and the more latent caloric will be evolved, and above the base of the cloud the air in ascending one hundred yards will cool only about one half as much as it would do if no vapor was condensed. Now, as the law of cooling on the outside of the ascending column is known to be about one degree for every hundred yards of ascent into the atmosphere, the temperature of the air in the inside of the ascend. ing column may be compared, at all its different heights, with the air on the outside; and consequently their relative specific gravities will thus be known. On making such comparison, Mr. Espy showed, that when the dew-point is very high, and the cloud thus formed of great perpendicular diameter, its specific gravity would be so much less than that of the surrounding air as to cause the barometer in extreme cases to fall nearly three inches, or about as much as it is known to do in great storms. The evolution of latent caloric, then, in the formation of cloud, Mr. Espy contends, is not merely a vera causa, but the sole cause of the fall of the barometer in storms, unless it shall be shown that this instrument sometimes actually falls more than three inches, which it has never yet been known to do. Mr. Espy then went on to show that his theory was demonstrated by three independent methods. First, by calculations founded on well known physical laws; second, by experi. ments with the nephelescope; and, third, by its ability to explain all the pheno. mena. Under the last head a few were mentioned which he deemed decisive of the question. The great degree of cold suddenly produced necessary to condense such immense quantities of vapor as are known to be condensed, in particular cases, can not be accounted for on any supposition but the up-moving current of air in the cloud. At Joyeuse, on the 9th of October, 1827, there fell over a small territory thirty-one inches of rain in twenty-two hours, and the latent caloric given out by the condensing vapor producing this rain, would be sufficient to heat the lower half of the atmosphere over the region where the rain fell about six hundred degrees. At the mouth of the Catskill, on the 26th July, 1819, there fell over a region of nine miles in diameter, ten inches of rain in half an hour, which would give out latent caloric enough to heat the lower half of the atmosphere two hundred degrees; or, in other words, would produce about the same effect in producing an up-moving as seven thousand tons of anthracite coal burnt in half an hour, over each square