Page:Popular Science Monthly Volume 20.djvu/434

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adepts in this fascinating study, and be has evidently spared no pains in preparing his manual, as his publisher has certainly spared no expense in illustrating it.




Education in Charleston, South Carolina. The Disabilities of the Unaided South in Public School Facilities. Published by the City Council. 1881. Pp. 32.

The Gesture Speech of Man. Address of Colonel Garrick Mallery, U. S. Army, before the American Association for the Advancement of Science. Salem, Massachusetts. 1881. Pp. 33.

The Duties of Women. By Frances Power Cobbe. Boston: George H. Ellis. 1881. Pp. 193. 25 cents.

Annual Report of the Surgeon-General of the U.S. Army. Washington. 1881. Pp. 23.

Reform in Medical Education. Annual Address before the American Academy of Medicine at New York. By Edward T. Caswell, M.D., President. Philadelphia. 1881. Pp. 16.

Circulars of Information from the Bureau of Education, No. 3. 1881. Washington: Government Printing-Office. Pp. 79.

Study of the Sphecidæ; List of the North American Larradæ; Notes on the Philanthinæ. By W. H. Patton. Pp. 28.

Education and Crime, pp. 10; The Discipline of the School, pp. 15. Bureau of Education. Washington: Government Printing-Office. 1881.

On the Filling of Amygdaloidal Cavities and Veins in the Keweenaw District of Lake Superior. By M. E. Wadsworth, Ph.D. Pp. 12.

The Areas of the United States: The Several States and Territories and their Counties. By Henry Gannett. E.M. Washington: Government Printing-Office. 1881. Pp. 20. With Map.

The Kinematics of Machinery. By Professor Alexander B. W. Kennedy, C. E. With an Introduction by Professor R. H. Thurston, C.E. New York: D. Van Nostrand. 1881. Pp. 88. 50 cents.

Malaria: What it Means and how Avoided. By Joseph F. Edwards, M.D. Philadelphia: Presley Blakiston. 1881. Pp. 81.

The Nature and Function of Art, more especially of Architecture. By Leopold Eidlitz. New York: A. C. Armstrong & Son. 1881. Pp. 493. $4.

The New Infidelity. By Augustus R. Grote. New York: G. P. Putnam's Sons. 1881. Pp. 101. $1.25.

Dangers to Health: A Pictorial Guide to Domestic Sanitary Defects. By T. Pridgin Teale, M.A. Third edition. Philadelphia: Presley Blakiston. Pp. 170. $3.50.

The Honey Ants of the Garden of the Gods, and the Occident Ants of the American Plain?. By Henry C. McCook. D.D. Illustrated. With Thirteen Plates. Philadelphia: J. B. Lippincott & Co. 1882. Pp. 188. $2.50.

Elements of Quaternions. By A. S. Hardy, Ph.D. Boston: Ginn & Heath. 1881. Pp. 230.

A Study of the Pentateuch for Popular Reading. By Rufus P. Stebbins, D.D. Boston: George H. Ellis. 1881. Pp. 233. $1.25.

Ecce Spiritus. A Statement of the Spiritual Principle of Jesus as the Law of Life. Boston: George H. Ellis. 1881. Pp. 238. $1.25.

Sparks from a Geologist's Hammer. By Alexander Winchell, LL.D. Chicago: S. C. Griggs & Co. 1881. Pp. 400. $2.

The League of the Iroquois and other Legends from the Indian Muse. By Benjamin Hathaway. Chicago: S. C. Griggs & Co. 1881. Pp. 319. $1.50.

Higher than the Church. An Art Legend of Ancient Times. By Wilhelmine von Hillern. From the German by Mary J. Safford. New York: William S. Gottsberger. 1881. Pp. 74.

Mechanics' Liens. How Acquired and Enforced. With an Appendix of Forms. By James T. Hoyt, of the New York Bar. New York: P. F. McBreen, printer. 1881. Pp. 310.

Zoölogical Atlas, including Comparative Anatomy, with Practical Directions and Explanatory Text. By D. M. Alpine, F.C.S. With 231 Colored Figures and Diagrams. Vertebra. Edinburgh and London: W. & A. K. Johnston. 1881.

Report upon United States Geographical Surveys west of the One Hundredth Meridian. Vol. VII, Archæology. By Frederick W. Putnam. Washington: Government Printing-Office. 1879. Pp. 497. Illustrated.



Finding the Center of Population.—The computation of the center of population of a country, as explained by Mr. F. D. Y. Carpenter, who has performed the work for the United States, for the census of 1880, is not a simple or an easy process. As defined in the "Statistical Atlas" of 1874, this center is the point at which equilibrium would be reached were the country taken as a plane surface, itself without weight, but capable of sustaining weight, and loaded with its inhabitants, each individual being assumed to be of the same gravity as every other, and consequently to exert pressure on the pivotal point directly proportioned to his distance therefrom. In other words, it is the center of gravity of the population of the country. It may be illustrated otherwise, by saying that it is the point at which, if all the population should assemble, the aggregate distance traveled by all those coming from any two opposite points of the compass would be respectively equal. It is found approximately by assuming a point as nearly as possible to the true position of the center, and then finding its north, south, east, and west moments of population; that is, the four aggregate products formed by multiplying the local populations by the distances of their centers north and south of the assumed parallel, and east and west of the assumed meridian. The sums of the north and south moments, and those of the east and west moments should be severally equal to each other. The differences which will appear between the several sums in the