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CONTENTS.

PAGE

I. Researches on the Hexatomic Compounds of Cobalt. By

Wolcott GIBBS, M.D. .......... 1

II. Contribntions to the Botany of North America. By Asa

GRAY:-

1. Synopsis of North American Thistles .....

2. Notes on Borraginacece . . . . . . . . . 48

3. Synopsis of North American Species of Physalis ..

4. Characters of various New Species .......

III. Graphical Integration. By EDWARD C. PICKERING . . 79

IV. On the Solar Motion in Space. By TRUMAN HENRY

SAFFORD .... ... ... .. . . . 82

V. Historical Sketch of the Generic Names proposed for Butter-

flies: A Contribution to Systematic Nomenclature. By

SAMUEL H. SCUDDER . . . . . . . . . . . 91

VI. On the Wide Diffusion of Vanadium and its Association with

Phosphorus in many Rocks. By A. A. Hayes, M.D. . 294

VII. Contributions from the Physical Laboratory of the Mas-

sachusetts Institute of Technology:-

1. Foci of Lenses placed Obliquely. By Prof. E. C.

PICKERING AND DR. Chas. H. WILLIAMS .. 300

VIII. Brief Contributions from the Physical Laboratory of Har-

vard College :-

1. On the Effect of Heat upon the Magnetic Suscepti-

bility of Soft Iron. By H. AMORY AND F. Minot 308

IX. A Conspectus of the North American Hydrophyllacea. By

Asa GRAY . . . . . . . . . . . . . . . 312

X. Revision of the Genus Ceanothus, and Descriptions of New

Plants, with a Synopsis of the Western Species of Silene.

BY SERENO WATSON .. ...... 333

XI. List of the Marine Algæ of the United States, with Notes of

New and Imperfectly Known Species. By W. G. FARLOW 351

XII. Brief Contributions from the Physical Laboratory of Har-

vard College :-

2. On a New Induction Coil. By John TROWBRIDGE 381

3. On the Effect of Armatures on the Magnetic State of

Electro-Magnets. By B. O. PEIRCE AND E. B.

LEFAVOUR. . . . . . . . . . . . . 385

4. On the Time of Demagnetization of Soft Iron. By

W. C. HODGKINS AND J. H. JENNINGS · · · 387

XIII. Contributions from the Physical Laboratory of the Mas-

sachusetts Institute of Technology :-

2. Light transmitted by one or more Plates of Glass.

By W. W. JACQUES ..........

XIV. On the Application of Logical Analysis to Multiple Algebra.

By C. S. PEIRCE . . . . . . . . . . . . . 392

XV. On the Uses and Transformations of Linear Algebra. By

BENJAMIN PEIRCE . . . . . . . . . . . . 395

XVI. Optical Notices. By Wolcott GIBBS, M.D. :-

1. On a New Optical Constant ........ 401

2. On a Method of Measuring Refractive Indices with-

out the Use of Divided Instruments . . . . . 417

XVII. Contributions from the Physical Laboratory of the Mas-

sachusetts Institute of Technology :-

3. Intensity of Twilight. By CHARLES H. WILLIAMS 421

4. Light of the Sky. By W.O. CROSBY ...425

5. Light absorbed by the Atmosphere of the Sun. By

E. C. PICKERING AND D. P. STRANGE ... 428

6. Tests of a Magneto-Electric Machine. By E. C.

PICKERING AND D. P. STRANGE . . . . . 432

7. Answer to M. Jamin's Objections to Ampère's Theory.

By William W. JACQUES ....... 445

XVIII. Melanosiderile: A New Mineral Species, from Mineral

Hill, Delaware County, Pennsylvania. By Josiau P.

COOKE, JR. · · · · · · · · · · · · · · · 451

XIX. On Two New Varieties of Vermiculites, with a Revision of

the other Members of this Group. By Josial P. Cooke,

JR., AND F. A. Gooch. . . . . . . . . . . 453

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OF THE

AMERICAN ACADEMY

ARTS AND SCIENCES.

VOL. X.
PAPERS READ BEFORE THE ACADEMY.

RESEARCHES ON THE HEXATOMIC COMPOUNDS OF

COBALT.*
By Wolcott GIBBS, M.D.

Presented, Oct. 13, 1874. In the joint memoir of Genth and myself on the ammonia-cobalt bases it was stated that xanthocobalt is not the only product of the action of nitrous acid gas upon ammoniacal solutions of cobalt. A further investigation of this and other related subjects was then promised. I propose now to resume the study of this class of compounds from the standpoint of the chemistry of the present day. The progress of science has rendered necessary the abandonment of my former theoretical views, as well as the adoption of the new notation. It has also, as I shall endeavor to show, lent a peculiar interest to the study of the ammoniametallic bases.

In studying the action of the alkaline nitrites upon salts of cobalt, or upon those of the different series of ammonia-cobalt compounds, a principal difficulty arises from the varying nature and relative proportions of the products obtained under various conditions of temperature, concentration of solutions employed, and duration of action. I have endeavored to cover the whole ground as completely as possible.

1. Action of Ammonia and Ammonic Nitrite upon a Solution of Cobaltic Chloride and Ammonic Nitrate. — When a warm solution of

* Being Part II. of Researches on the Ammonia-cobalt Bases, by Wolcott Gibbs and F. A. Genth.

VOL. X. (n. 8. 11.)

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