Page:Popular Science Monthly Volume 16.djvu/144

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134
THE POPULAR SCIENCE MONTHLY.

Wonders of the Flora. By H. A. Kresken. Dayton, O. 1879. Pp. 204. $1.50.

The Rosicrucians, their Rites and Mysteries. By Hargrave Jennings. With numerous Illustrations. New York: J. W. Bouton. 1879. Pp. 388.

Report of the Commissioner of Education for the Year 1877. Washington: Government Printing-Office. 1879. Pp. 850.

First Step in Chemical Principles. By H. Leffmann, M. D. Philadelphia: E. Stern & Co. 1879. Pp. 52. 50 cents.

Ancient Pagan and Modern Christian Symbolism. By Thomas Inman, M. D. With Illustrations. New York: J. W. Bouton. 1850. Pp. 147.

Lessons in Inorganic Chemistry. By W. G. Valentin. With Illustrations. New York: Putnam's Sons. 1879. Pp. 186. $1.

Report on Copper-Tin Alloys. By R. H. Thurston. Washington: Government Printing-Office. 1879. Pp. 800.

Local Government. By R. P. Porter. From "Princeton Review." Pp. 24. 5 cents.

The Public Library and the Common Schools. By C. F. Adams, Jr. Boston: Estes & Lauriat. 1879. Pp. 52. 25 cents.

The South Pass Jetties. By M. E. Schmidt. From "Transactions of the American Society of Civil Engineers." Pp. 36, with Plates.

Address to the New Orleans Sanitary Association. By Dr. J. H. Ranch. Pp. 13.

Domestic Sanitation. New Orleans: Graham Print. 1879. Pp. 20.

Milk and Dairies in New Orleans. New Orleans: Rivers Print. Pp. 16.

Tracheotomy with Galvano-Cautery. By Dr. W. A. Byrd. From "St. Louis Clinical Record." Pp. 7.

Shall the Metric System be made compulsory? By H. T. Blake. From "The New-Englander." Pp. 22.

Petroleum. By P. Schweitzer. Columbia, Mo.: "Statesman" Print. 1879. Pp. 64.

Report of the Entomologist. By C. V. Riley. Washington: Government Printing-Office. 1879. Pp. 52, with Plates.

Phenol. By David Cerna. From "Philadelphia Medical Times." Pp. 5.

American Industries and the Proposed Franco-American Commercial Treaty. San Francisco: "Alta California" Print. Pp. 211.

History of Massage. By D. Graham, M.D. New York: W. Wood & Co. 1879. Pp. 80.

The Pocasset Tragedy. By W. Denton. Boston: The Author. 1879. Pp. 33.

Biographical Notice of Joseph Henry. By Joseph Lovering. Pp. 11.

Sanitary Condition of Montreal. By F. P. Mackelcan, C.E. Montreal: Lovell Print. 1879. Pp. 41. 10 cents.

The More Common Families of Insects. By L. C. Wooster. Whitewater, Wis.: "Register" Print. 1879. Pp. 52.

 


POPULAR MISCELLANY.

Experiments with Platinum.—A paper by Mr. Edison, on the behavior of platinum under the influence of the electric current, was read at the last meeting of the American Association by Professor F. R. Upham, the author being absent. Having found that a platinum wire, heated by the electric current and suspended in the air, loses weight in proportion to its mass, its heat, and the length of time during which the current passes through it, Mr. Edison took a platinum wire 201000 of an inch in diameter, and wound it in the form of a spiral one eighth of an inch in diameter and one half inch in length. The two ends of the spiral were secured to clamping-posts, and the whole then covered with a small glass shade. After the spiral had been made incandescent for twenty minutes, the shade opposite to the spiral on both sides was slightly darkened, and after five hours was no longer transparent, a film of the metal having been deposited on it. Mr. Edison is convinced that this effect, namely, the loss of weight in the spiral, is due to the washing action of the air, to the wearing away of the surface of the platinum by the impact of the stream of gases upon the highly incandescent surface, and not to volatilization. That this supposition is correct is shown by the very different behavior of platinum wire in vacuo. Mr. Edison placed a spiral of platinum in the receiver of a common air-pump, and arranged it so that the current could pass through it while the receiver was being exhausted. At the pressure of two millimetres the spiral was kept incandescent for two hours before the deposit on the glass shade became visible. In another experiment, when the exhaustion was higher, the deposit became visible only after five hours. The same paper contained observations on other phenomena of still greater interest. It has been known for some time that platinum, when long subjected to a high temperature, becomes disintegrated. A platinum wire which has been heated to incandescence for twenty minutes, on being examined under a microscope, is seen to be full of cracks, and appears shrunken. If the current is continued for a considerable time the wire will fall to pieces. Now, Mr. Edison finds that this shrinking and cracking of the wire are due entirely to the expansion of the air in the pores of the metal, and its contraction on the escape of the air. If these air-spaces be previously eliminated, the platinum can be heated to incandescence without disintegration. How this is to be done is best told in Mr. Edison's own words: