an increased transpiration was necessary, but was always checked by the increased pressure of vapor in the middle of the day; this of course deranged the circulation and caused the liquids in the circulation to begin to ferment. This view is supported by the fact that in Holland the parts first attacked were the leaves and stalks, the parts more directly in contact with the air. In Scotland and some parts of Prussia the disease made its appearance in September, for the most part; the temperature of the earth was then higher than that of the air, and accordingly the disease generally attacked the tubers first. But when we acknowledge all of these extraordinary facts, we still are forced to look for some special predisposition to disease among the potatoes themselves. In what this special predisposition consists, it is not easy to say.

It has not been the same in all species of potatoes, some have almost escaped while others of another kind in the same neighborhood have been almost utterly destroyed; it must reside in the plant itself, either in the structure of its tissues, or in the chemical state of its juices. It has been noticed that the potatoes of late years have had a much greater tendency than usual to germinate. This indicates an unusual molecular movement in the juices, which under the influence of moisture and the atmosphere, in place of changing the starch into dextrine and dextrine into cellulose, ferments and causes the disease.

Potatoes planted during the early morning have in some instances been almost entirely free from the malady, while those of the same variety planted in the afternoon, after lying in the sun sometime, were almost all destroyed. In this case, it seems possible that the heat of the sun gave a movement to the juices and prepared the way for the subsequent attack.

Von Martius describes two distinct kinds of disease, De Drooge kankerachtige Ziekte der Aardappelen, the dry canker disease of the potatoe, Gangræna tuberum Solani; and "De schurftachtige Ziekte der Aardappelen," the scabby disease of the potatoe, Porrigo tuberum Solani.

Prof. Harting's results and suggestions certainly furnish ample ground for very probable theories as to the cause of this disease, and indicate the course to be taken in future investigation. If, as seems possible, atmospheric influences induce such chemical changes in our growing crops, though we have found a cause, we have not found a remedy; to guard field crops from atmospheric changes is not an easy matter.

Such changes may occur only at long intervals of years, but the fact of their occurring at all, will be a warning to the nations not to place their sole dependence on a single crop. Unhappy Ireland and the north of Scotland are mournful examples of this mistake. J. P. N.

Utrecht, April 25, 1847.

SECOND SERIES, Vol. IV, No 10.-July, 1847.

10

ART. X.-Report on Meteorites; by CHARLES UPHAM SHEPARD, M.D., Professor of Chemistry in the Medical College of South Carolina, and in Amherst College, Mass.

(Continued from Vol. ii, ii Ser., p. 392.)

CLASS II. METALLIC.

ORDER FIRST. Malleable, homogeneous.
Section 1st. PURE.

1. Walker county, Alabama.-This mass was described by Dr. TROOST in Vol. xlix, p. 344, (1845.) Through the assistance of Dr. I. F. SOWELL, of Athens, Ala., I am able to supply a few additional details, concerning the occurrence of this unusually interesting specimen. Dr. Sowell observes, that "the existence of this iron was made known to me in 1839 or '40; and I was in treaty for it during two or three years, before being able to obtain possession of it. The original mass was irregularly oval, resembling the figure here sketched.

Fig. 6.

"It was without any abrupt prominences or depressions, and was covered by a smooth, black crust. It was found with the larger end buried in the ground, leaving a portion of the smaller extremity projecting above the soil,-suggesting the idea, that it was driven into the ground by the force of its fall. Upon this small

er end, the finder (Mr. Speaks) placed his foot to rest, while abroad on a hunting excursion. Its unusual appearance attracted his attention, and led him to remove it to his house as something valuable. The mass was found remote from any settlement, in an uncultivated and rather unfrequented region. Its weight was one hundred and sixty-five pounds."

This iron does not afford by etching, the Widmannstättian figures; although it exhibits glistening freckles, or angular spots of the size of fine-grained gunpowder, which are occasionally intermingled with shining lines and fibres. Sp. gr.=7.265.

It consists of iron 99-89, with traces of calcium, magnesium and aluminium, in the order, as to quantity, in which they are enumerated, the calcium being most abundant.

2. Scriba, (Oswego,) N. Y.-My description of this mass was published in Vol. xl, p. 366, (1841.) To that account may now be added the statement of Mr. John G. Pendergast, communicated to me in a letter dated July 15, 1846. "I saw a mass of iron at Oswego in 1834, in the possession of Mr. Rathbun, (a blacksmith,) which I judged to be meteoric. Mr. R. had obtained it on that day from his collier, who had been down to deliver a load of charcoal, and stated that he found it in the woods, some where in the vicinity of his coal-pit. The circumstance of its being found in the forest, together with its size and form, induced me at the time to believe it to be meteoric iron. The mass in all probability, was originally globular in form, but from having been highly ignited, and striking the earth (perhaps on a stone) with great force, a flattening in its shape was produced, like that which would be occasioned in a round lump of putty, if thrown against a board. I was fully satisfied that the form it possessed, could have been imparted in no other way."

The foregoing contains but little beyond the testimony of a second witness, to the conditions under which the mass was found. It appeared important however, to omit no circumstance relative to its discovery, for the reason that it does not possess that peculiar chemical composition, which has heretofore been regarded as confirmatory of the extra-terrestrial origin of similar productions, and on which account, I hesitated in my first notice to include it among undoubted meteoric irons. Its resemblance however, to the Walker county, Ala., iron, not only in composition, but in the generally smooth surface and black color of its crust, and still more, in the freckled figures developed upon its polished sections by nitric acid, establishes an analogy of the most marked kind between the two bodies. And as it seems unreasonable to ascribe the large drop-shaped mass of Alabama, either to a terrestrial or an artificial source, I feel authorized in claiming a meteoric origin for them both.

Section 2d. ALLOYED. Sub-section, CLOSELY CRYSTALLINE.

3. Babb's Mill, 10 miles north of Greenville, Green county, Tennessee. This mass was described by Dr. TROOST in Vol. xlix, p. 342, (1845.) Judge PECK has afforded me (under date of Dec. 14, 1845) some additional particulars, relating to the locality, from whence he had obtained a specimen, in its natural condition. His remarks are as follows: "Of the two masses found in Green county, the first, as well as I can recollect, weighed twelve or thirteen pounds; the other which I have, weighs upwards of six pounds. The former was injured by having been heated and cut. It exhibited however, a crystalline structure, when small portions were torn or broken asunder, though the grains were very small. It was homogeneous; and formed as malleable and tough an iron, as I have ever seen. The second mass (of about six pounds) I was fortunate enough to obtain, just as it was found."

This specimen was in the most obliging manner transferred to me, in exchange, by Judge Peck; and with the exception of a few hundred grains taken from an angle, has been preserved precisely in its original shape. It exhibits in the most perfect manner that peculiar moulding (consisting of somewhat irregular basin-shaped depressions of various sizes, connected with blunt rounded angles and edges) which marks so many of these productions. A wood-cut does but inadequately render these appa

*Having observed that this kind of surface occurs in masses of artificial iron, both cast and malleable, if it have been a long time exposed to the action of weather, (as in iron palings and posts, as well as in old cannon,) I cannot avoid attributing the pitted, indented outside of the meteoric irons, in part, to terrestrial influ

rent. The black coating of oxyd of iron, so often investing meteoric iron, is here nearly replaced by broad patches of a thin, yellowish, ochrey brown incrustation.

Sp. gr. =7-548. It is close grained and perfectly compact, taking a very high polish, and exhibiting at the same time, a color rather whiter than that of steel. It shows no crystalline figures on being corroded with nitric acid; although on very close inspection, minute, whitish spots, (isolated and collected into patches,) may be seen here and there, scattered without order over the surface. When broken, it presents a fine granular texture, attended by a high silvery lustre.

Dr. TROOST found the mass he obtained to contain, iron 87-58, nickel 12-42, remarking however that the ratio of the nickel given was probably too high, and that the compound might contain other ingredients. My own specimen affords me, iron 85-30, nickel 14.70, with traces of calcium, magnesium and aluminium. 4. Claiborne, Alabama.-Vol. xxxiv, p. 332, (1838.) Vol. xlviii, p. 145, (1845.)

5. Livingston county, Kentucky.—Vol. ii, ii Ser., p. 357, (1846.) 6. Dickson county, Tennessee.-Vol. xlix, p. 337, (1845.)

7. Texas, (Red River.)—Vol. iii, p. 44, (1821.) Vol. viii, p. 218, (1824.) Vol. xvi, p. 217, (1830.) Vol. xxvii, p. 382, (1835.) Vol. xxxiii, p. 257, (1838.) Vol. xliii, p. 358, (1842.) Vol. ii, ii Ser., p. 372, (1846.)

8. Burlington, Otsego county, N. Y.-This mass (originally 150 lbs. in weight) was described by Prof. SILLIMAN, Jr., in Vol. xlvi, p. 401, (1844.) It was ploughed up by a farmer, near the north line of the town, sometime prior to 1819. Portions were cut from it, from time to time, by the discoverer's blacksmith, for agricultural uses; until its weight was diminished to about a dozen pounds, when it fortunately fell into the hands of Prof. Hadley, of Geneva, N. Y., to whom I am indebted for a conical lump, (weighing nine pounds,) which must have formed a somewhat pointed extremity of the original mass. From the base of this, a slice was taken, leaving a lump of five pounds of the annexed form. Its sides show for the most part, the natural crust of the iron; but where this is not the case, the surface has been cut and polished, or is coarsely crystalline with large tetrahedral and sub-hackley faces, occasioned by the breaking off of what were apparently projecting prongs. Its polished faces show a very high lustre, with a color of nearly the same whiteness as German silver. Held at a proper angle, they discover very distinctly the same crystalline characters, which are still more distinctly brought out by the ac

ences, which have acted upon masses not perfectly homogeneous either in composition or in density. For this reason perhaps, the Lockport iron, which is very much charged with amygdaloidal kernels of magnetic iron pyrites, presents an uncommonly pitted and jagged surface.