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the temperature of melting ice fourteen and four thousand five hundred and twenty-one ten-thousandths grams in mass, of a constant cross-sectional area, and of the length of one hundred and six and three-tenths centimeters.

Second. The unit of current shall be what is known as the international ampere, which is one-tenth of the unit of current of the centimeter-gram-second system of electro-magnetic units, and is the practical equivalent of the unvarying current, which, when passed through a solution of nitrate of silver in water in accordance with standard specifications, deposits silver at the rate of one thousand one hundred and eighteen millionths of a gram per second.

Third. The unit of electro-motive force shall be what is known as the international volt, which is the electro-motive force that, steadily applied to a conductor whose resistance is one international ohm, will produce a current of an international ampere, and is practically equivalent to one thousand fourteen hundred and thirty-fourths of the electro-motive force between the poles or electrodes of the voltaic cell known as Clark's cell, at a temperature of fifteen degrees centigrade, and prepared in the manner described in the standard specifications.

Fourth. The unit of quantity shall be what is known as the international coulomb, which is the quantity of electricity transferred by a current of one international ampere in one second.

Fifth. The unit of capacity shall be what is known as the international farad, which is the capacity of a condenser charged to a potential of one international volt by one international coulomb of electricity.

Sixth. The unit of work shall be the Joule, which is equal to ten million units of work in the centimeter-gram-second system, and which is practically equivalent to the energy expended in one second by an international ampere in an international obm.

Seventh. The unit of power shall be the Watt, which is equal to ten million units of power in the centimeter-gram-second system, and which is practically equivalent to the work done at the rate of one Joule per second.

Eighth. The unit of induction shall be the Henry, which is the induction in a circuit when the electro-motive force induced in this circuit is one international volt while the inducing current varies at the rate of one Ampere per second.

Sec. 2. That it shall be the duty of the National Academy of Sciences to prescribe and publish, as soon as possible after the passage of this Act, such specifications of details as shall be necessary for the practical application of the definitions of the ampere and volt hereinbefore given, and such specifications shall be the standard specifications herein mentioned.

To meet this requirement of Congress, it was necessary, in accordance with the constitution of the National Academy of Sciences, to appoint a special committee to consider the subject. This was done as soon as an official copy of the law was received from the State Department. The committee, selected from members of the National Academy, was as follows :

Prof. H. A. ROWLAND, Chairman, Johns Hopkins University, Baltimore.
Gen. H. L. ABBOT, United States Engineers, New York.
Prof. G. F. BAKKER, University of Pennsylvania, Philadelphia.
Prof. J. TROWBRIDGE, Harvard University, Cambridge.
Prof. C. S. HASTINGS, Yale University, New Haven.
Dr. C. BaRus, Smithsonian Institution, Washington.
Prof. A. A. MICHELSON, University of Chicago, Chicago.

The committee completed the work assigned to them, and the specifications they prepared meet the requirement of the law, and are also in accord with international agreement.

The report of this committee, approved by all its members, was submitted to the National Academy of Sciences at a special

meeting held in New York, on the 9th of February, 1895, and was then unanimously adopted by the Academy.

At the same session, the National Academy of Sciences voted to prescribe and publish the specifications relating to the ampere and volt, as required by the above law.

To secure the necessary publication of these results, it was also voted, that the President of the Academy send a copy of the specifications to each house of Congress, and to the Secretary of State, with the request to the latter that they be issued by the State Department; and further that the Academy print a suitable number for public distribution. Certified copies have already been transmitted to Congress, and to the State Department, and the official copies to be distributed by the National Academy will soon be issued.

This action of the National Academy of Sciences completes the law of July 12, 1894, and makes the legislation of the United States on the standards for electrical measure in advance of that of any other nation.-0. C. M.

New Haven, Conn., Feb. 20, 1895.

11. Physics for University Students; by Henry S. CARHART. Part I, Mechanics, Sound and Light. 344 pp. Boston, 1894 (Allyn & Bacon).—This brief and concise text-book has been prepared by the author to be used by his students in connection with the formal course of lectures by which they are introduced to'the subject of general physics; other teachers similarly situated may well find that it also meets their needs. The subjects are for the most part presented clearly; a sufficient number of suitable illustrations accompany the text. The volume is about equally divided between mechanics, sound and light; the subject of light would seem to have deserved relatively a somewhat greater space than sound.

II. GEOLOGY AND MINERALOGY. 1. The correlation of the Bohemian and Eifiliun divisions of the Devonian.* As the result of observations made in the neighborhood of Prague and the examination of the original collec. tions of the Bohemian fossils the authors have made a comparison of the faunas of the Barrandian zones F. G. and H. with the faunas of the typical Eifelian Devonian.

They show that the Greifenstein limestone of the Rhine contains a fauna equivalent to the Bohemian fauna of the Mnenjan limestone, which is above and distinct from that of the Konjeprus limestone. The latter limestone is shown to be the equivalent of the Hercynian limestone of the Hartz and thus they prove the Greifenstein limestone to belong above in the Middle Devonian as an equivalent of the Eifelian Cultrijugatus beds. They restrict the use of the term Hercynian to the calcareous beds of the lower

* Ueber die stratigraphis hen Beziehungen der böhmischen Stufen F. Gs. H. Barrandes zum rheinischen Devon. von E. Kayser in Marburg u. E. Holzapfel in Aachen, Jabrb. d. k. k. geol. Reichsanstalt, 1894, vol. xliv, Heft 3, pp. 479-514.

wieder Schiefern" of the Hartz and formations in other regions bearing the same fauna. This limestone, according to their present opinion, is scarcely older than the unter-Coblenz or the highest of the Siegener Schichten. The equivalents of the Hercynian, so restricted, are the Konjaprus limestone of Bohemia, the Erbray limestone of France, the Ural limestone of Bjelaja river, Russia, and the Lower Helderberg of America.

The following scheme presents the correlations of the Bohemian zones, through the Hessen Nassau sections, with the standard Eifelian formations :

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This determination, it will be noticed, restricts the Bohemian formations G and H to the Middle Devonian, and draws the line between the Greifenstein and Mnenian faunas, which are regarded as equivalent to the Cultrijugatus beds, and the typical IIercynian fauna of Lower Devonian age. The paper is an excellent illustration of the accurate correlation to be attained by a critical comparative study of local faunas.

H. S. W. 2. Daimonelix of the Lacustrine Miocene of Nebraska.-Under the name of Daimonelix, Prof. E. H. BARBOUR has described in the “University Studies” of the University of Nebraska for 1892 and 1894, large open coils occurring in the Nebraska Miocene; the paper is accompanied by many excellent figures, some of them from photographs. The fossils had been called Devil's corkscrews and hence the name which he gives them. The coils stand vertically at different heights in a bed about 100 feet thick, and are ordinarily 6 to 8 feet high, though ranging up to over 12 feet, with the thickness of the stem of the coil 2 to 8 inches. The basal portion is extended out laterally, with a rising curve, to a length sometimes of 13 feet, and has a varying diameter of 6 to 10 inches. The coils are both right handed and left handed; and sometimes they are double.

They were first thought by Prof. Barbour to be fossil freshwater sponges; but possibly burrows of Rodents which had become filled with sand,--the bones of a Rodent having been found in the base of one of the coils. In his later paper, of July, 1894, he states, on the ground of new observations, that the interior structure of the coils is coarse cellular; and that the surface is one tangle of ramifying, intertwining tubules, of a diameter from one sixty-fourth to one-eighth of an inch; some are full a fourth of an inch, but the average is about a thirty-second of an inch.” “ The tubules grow more densely clustered as we pass inward, and finally, as it were, thicken into a white solid compact wall” which in some cases is nearly an inch thick. The conclusion is thence reached that the coiled fossils were some kind of plant.

Prof. J. A. Allen, of the American Museum of Natural History, judging from the descriptions in the paper of 1892, expressed the opinion in the letter to the writer, that they were probably the burrows of a Rodent, one or more species of Rodent having been described from the Miocene beds.

Prof. W. G. Farlow of Cambridge, in view of the later as well as earlier described facts, writes rejecting the idea as to their being Alge or of any other order of Cryptogams, and says, in conclusion that “on the whole, in spite of the failure of the microscopic sections to show the characteristic structure of roots, I cannot help believing that the coils were really hollows into which something like roots have grown and been fossilized. It would be of great interest to have a microscopic examination of the matrix in which the coils are imbedded; for it might afford a clew as to the possible nature of the filaments of which the coils are mainly composed.”

This conclusion of Prof. Farlow is consistent with that of Prof. Allen, that they are probably the burrows of Rodents, and that the winding form of the burrow was adopted, as the latter suggested, to facilitate ascent and descent.

J. D. D. 3. Report of the geological survey of Ohio, Vol. VII., Economic Geology, Archäology, Botany, Paleontology, pp. i-xvi, i-290, i-700, Plates I-LVI. A colored geological map of the state, 10 folio maps illustrating the coal fields, several woodcuts in the body of text and 11 charts and maps illustrating Archæology. 1893.—The volume is divided into two parts: Part 1-Economic -contains chapters on the geological scale and geological structure of Ohio, ihe clays of Ohio, their origin, composition and varieties, and the coal fields of Ohio, by Prof. Edward Orton, and one on The clay working industries of Ohio, by EDWARD ORTON, Jr In the first chapter the state geologist calls attention to the importance of retaining the original boundaries of the Waverly group, the lowest member of which is the Bedford shale of Newberry of the northern part of the state, the name Waverly shale having been applied to the extension of the same formation in the southern part of the state. The Obio shale, including the Huron, Erie and Cleveland shales of Newbury “fills the entire interval between the Hamilton proper and the Catskill group, and in the judgment of some geologists a wider interval even than that named above.

Part II contains the following chapters: Chapter I, The Archeology of Ohio, an abstract embodying the principal results of explorations and discoveries thus far made, designed for those to

whom the hitherto published literature of the subject is not easily accessible, by GERARD FOWKE; Chapter II, Catalogue of Obio Plants, by W. A. KELLERMAN and Wm. C. WERNER. Besides the list itself (pp. 81-406) this article includes a valuable Bibliography of Ohio Botany from 1815-1893. Chapter III, on Paleontology, contains contributions to the Paleontology of Ohio, by R. P. WHITFIELD; 1. Descriptions of fossils from the Paleozoic rocks of Ohio (reprinted' from Am. N. Y. Acad. Science, Vol. V, read Oct. 13, 1890). Plates I-XIII accompany this paper. Chapter IV, Observations upon the so-called Waverly group of Ohio, by C. L. HERRICK, pp. 495-515, Plates XIV-XXIV contain an introduction and brief summary of results already published in the Bulletins of Denison University, the Am. Geologist, and Bulletins of the Am. Geol. Society. The author still holds the view that the Berea grit is the real tloor of the Carboniferous series—" pot necessarily the base of the Carboniferous, but the most convenient base line for the Waverly," remarking that a study of localities “and collections on which Dr. Newberry's opinion that the Bedford shale fossils are Carboniferous] was founded has convinced the writer that these species do not occur in the typical Bedford, but in thin tlags associated or interbedded, while the typical Bedford, especially in central Ohio, where it reposes directly upon the ‘Black shale,' carries a considerable series of fossils forming a decidedly Devonian assemblage.”—(p. 507). In a critical case like this, it is unfortunate that so keen an observer as Professor Herrick should describe as "typical Bedford ” a formation which confessedly does not contain the typical fossils of the Bedford shale. Chapter V, Fossils of the Clinton group in Ohio and Indiana, by AUG. F. FOERSTE, is apparently a republication of the author's paper on this subject which appeared in the Bulletins of Denison University. It is accompanied by plates XXV-XXXVIla. Chapter VI contains The Fossil Fishes of Ohio, by E. W. CLAYPOLE, with a supplement by A. A. Wright, on the ventral armor of Dinichthys. Plates XXXVIII-XLIV accompany this chapter. The final chapter, VII, is entitled, New and little known Lamellebranchiata from the Lower Silurian rocks of Ohio and adjacent states, by E. (. ULRICH. This paper is illustrated by a fine series of plates, XLV-LVI, prepared by the author. H. S. W.

4. Geological and natural history survey of Minnesota. 22d Annual Report for the year 1893. pp. 210, 1894.—This Report gives account of the final field work of this survey. The state geologist, Winchell, makes the statement that there remains still to be published the third volume of the Final Report, which is in preparation and several Chapters of which have been already printed, and preliminary copies distributed. The following papers are included:-Summary statement; List of rock samples col. lected to illustrate the notes of N. H. WINCHELL, 1893 ; Preliminary report of field work during 1893 in northeastern Minnesota, chiefly relating to the glacial drift, by WARREN UPHAM; Pre

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