the lines, resembling the representation we have of the etched surface of Hauptmannsdorf iron. Schreibersite is visible in the iron, but so inserted in the mass, that it cannot be readily detected by mechanical means. Hydrochloric acid leaves a residue of beautifully brilliant patches of this mineral.

Subjected to analysis, it was found to contain

The iron is remarkably free from other constituents. It is especially interesting as the largest mass of meteoric iron in this country next to the Texas meteorite at Yale College.

4. Meteoric Iron from Tucson, Mexico.

We have had several accounts of meteoric masses which exist at Tucson; Dr. J. L. LeConte having made them known some few years ago. Since that time Mr. Bartlett, of the Boundary Commission, has seen them and made a drawing of one which he has kindly allowed me the use of, as well as the manuscript* notice of them, which is however, quite brief. This mass is used for an anvil, resembles native iron, and weighs about six hundred pounds. Its greatest length is five feet. Its exterior is quite smooth, while the lower part which projects from the larger leg is very jagged and rough. It was found about twenty miles distant towards Tubac, and about eight miles from the road where we are told are many larger masses. The following figure (3) represents the appearance of that meteorite.

Since my communication last April, I have obtained fragments of the meteorite from Lieut. Jno. G. Parke, of the U. S. Topographical Engineers, who cut them from the mass at Tucson, and to whose kindness I feel much indebted.

Some of the fragments were entirely covered with rust, and in some parts, little blisters existed, arising from chlorid of iron. Portions of the broken surface retain their metallic lustre untarnished. The Widmannstättian figures are very imperfectly developed, owing to the porous nature of the iron, the pores of which are filled with a stony mineral. The specific gravity taken on three specimens were 6·52—6·91—7·13. The last was the most compact and free from stony particles that could be found, and upon that the chemical examination was made.

* Since this was communicated to the American Association for the Advancement of Science, Mr. Bartlett's valuable and instructive work, entitled "Personal Narrative of Explorations in Texas, New Mexico, California, Sonora, and Chihuahua," has been published in two handsome octavo volumes, by the Messrs. Appleton's, New York: and we are indebted to the publishers for the use of Mr. Bartlett's fine cuts on the following pages.-J. L. S.

SECOND SERIES, Vol. XIX, No. 56.-March, 1855.

21

On examination it is seen to consist of two distinct parts, metallic and stony; the latter was only in minute particles, yet it was impossible, among the specimens at my disposal, to find a piece that was without it. On analysis, the following ingredients were found:

Some few particles of olivine were separated mechanically, and readily recognised as such under the magnifying glass in connection with the action of acids, which readily decompose it, furnishing silica and magnesia. Some of the olivine is in a pulverulent condition, resembling that of the Atacama iron. The nickeliferous iron of this Tucson meteorite also resembles that of the Atacama iron; calculated from the above results, it consists of

Iron 90-91, nickel 8.46, cobalt 63, copper, trace=100.00. This meteorite is one of much interest, and it is to be hoped that some of our enterprising U. S. Topographical Engineers

Since my notice of this meteorite, Prof. C. U. Shepard has published (Am. Journal of Science, Nov. 1854) an account of it, not aware of my communication to the Am. Assoc. He seems inclined to think that the stony material might be chladnite, although he could form no definite conclusion on this head. From what has

will yet be able to persuade the owners to part with it and bring it to this country.

5. Meteoric Iron of Chihuahua, Mexico.

For the description of this meteorite, I am indebted to the manuscript of Mr. Bartlett, and had hoped to have obtained a fragment of it for examination from Dr. Webb, who detached pieces from the mass; but when applied to, they were no longer

in his possession. It exists at the Hacienda de Conception, about ten miles from Zapata. "The form is irregular. Its greatest height is forty-six inches; greatest breadth thirty-seven inches; circumference in thickest part eight feet three inches. Its weight as given by Senor Urquida, is about three thousand eight hundred and fifty-three pounds. It is irregular in form, as seen by the figure; and one side is filled with deep cavities, generally round and of various dimensions. At its lower part, as it now stands, is a projecting leg, quite similar to the one on the meteorite at Tucson. The back or broadest part is less jagged than the other portions, and contains fewer cavities, yet, like the rest, is very irregular."

been said in the text, it will be seen to be olivine, the chladnite of the Bishopville stone not being attacked by acid, or only to a very feeble extent, by boiling sulphuric acid. And I would here remark that from some investigations just made, chladnite is likely to prove a pyroxene.-J. L. S.

ART. XVI.-On the Periodical Rise and Fall of the Lakes; by MAJOR LACHLAN, Montreal.

(Continued from p. 71.)

SUCH continued to be the state of the question, till the institution, by the American States, of those great patriotic works, the Geological Surveys of New York, Ohio, and Michigan, when the subject being taken up by the talented individuals employed in that duty, as far as their other immediate avocations would permit, with that spirit which ever distinguishes the lovers of science, I was enabled to glean many interesting additional particulars from their official reports, though, unfortunately, none sufficiently conclusive to solve the great philosophical problem so long under discussion. Among these I, of course rank first the eminent American geologist, Professor Hall, from whose elaborate work, put forth under the enlightened auspices of the State of New York, I extract the following valuable remarks on the elevation and depression of the great Lakes:*

"The fluctuating level of the waters of these Lakes has long excited attention; and many speculations have been hazarded to account for the phenomenon. The somewhat general belief that the periodical rise and fall in their waters occupy seven years appears not to be founded on authentic observation. Sand-bars and beaches, or the inlets of certain bays, are regarded as the landmarks; and these being liable to fluctuation from accumulation and removal, it follows that no hypothesis, founded on such observations, can be of any value. . . It is nevertheless true that there are important fluctuations in the Lake levels, which are unconnected with the temporary influence of winds. The only rational explanation of these changes yet afforded is that depending on the waste and supply of water. From the immense surface exposed to the sun's rays, it is plain that the amount of water evaporated is immense; and if by any means the process becomes retarded, the water is elevated. Again, the greater quantity of snow fallen during certain seasons has been considered a sufficient reason for explaining the increased elevation of the Lakes. If after such a season a summer follows when there is a small degree of sunshine, the amount of evaporation being thus diminished, the Lakes remain at a high point. These causes, though perhaps satisfactory, and without doubt true, at least to a certain extent, do not always appear sufficient to account for the fluctuations which have been noticed. Twenty-five or thirty years ago the beach of Lake Erie was a travelled highway beyond Buffalo; but at this time it would be quite impossible to travel along the same.

* See Hall's Geology of New York, pp. 408 to 410.

"From the united testimony of persons residing along the margins of all the Lakes, and from other demonstrative proofs, it appears that for many years previous to 1838, all the Lakes had been rising, that about that time they attained their maximum, and have since (to 1842) been subsiding. I have no means of determining the time or degree of the minimum depression. Mr. Higgins, the State Topographer of the Geological Survey of Michigan, gives the rise of the Lakes as five feet from 1819 to 1838, and regards it as probable that the minimum period continues for a considerable length of time, while the maximum continues only for a year. A single individual has informed me that about 1788 or 1790 the Lakes were nearly as high as in 1838.

.

"The annual fluctuations in the level of the Lakes are doubtless due to the nature of the seasons, depending on the quantity of rain and snow, and the amount of the evaporation; but it is not so satisfactorily demonstrated that for a series of twenty years the quantity of rain and snow has increased, or that evaporation has lessened uniformly throughout that period.

"The effect of winds in producing (daily) temporary elevations and depressions is very remarkable. A strong westerly wind. will raise the water in the eastern end of Lake Erie several feet in a few hours, when a much larger quantity is driven down the Niagara; and although so rapid a stream below the Falls, the water frequently rises fifteen or twenty feet during a westerly wind. At the same time the water is diminished at the western extremity of the Lake, and a corresponding depression there takes place. The prevalence of a strong easterly or northerly wind in the same way drives the waters to the western and southern parts of the Lake, and a much smaller quantity flows down the Niagara during such period. The same effects take place in a greater or less degree in all the Lakes-the rising at one extremity and the sinking at the other, till the wind subsides, when it resumes the equilibrium, and in so doing presents a beautiful exhibition of the long swells which are observed in the ocean after the subsidence of a high wind."

Professor Hall was well seconded by Professor Mather, afterwards chief director of the Geological Survey of Ohio, and subsequently (in 1845, '46, and '47) a resident on the shores of Lake Superior, observant of the meteorology and change of level of that Lake, from whose reports and other writings I extract the following particulars respecting Lakes Erie and Superior:*

"A tradition exists that there is a periodical rise and fall in Lake Erie, through a certain number of years. If it is true-and there are reasons for believing that it may be so, to a certain extent

* See Geological Report of Professor Mather for 1838.