374 



THE POPULAR SCIENCE MONTHLY 



pairing its scientific accuracy, make it easy 

 for the general reader. It would have been 

 improved in this respect, however, had a 

 glossary been appended. A few examples 

 of want of care in the use of classificatory 

 terms, and occasional indications of care- 

 less proof-reading, are blemishes that may 

 be corrected in a second edition. 



PUBLICATIONS EECEIVED. 



Report of the Commissioners of Agricult- 

 ure for 18*72. 



Practical and Critical English Grammar. 

 By Noble Butler. Louisville, Ky. : Morton 

 & Co. Pp. 312. Price, $1.00. 



Polarization of Light. By W. Spottis- 

 woode, F. R. S. New York : Macmillan. 

 Pp. 130. Price, $1.00. 



Organic Chemistry. By W. Marshall 

 Watts. New York : Putnam's Sons. Pp. 

 130. Price, 75 cents. 



Practical Theory of Voussoir Arches. 

 By William Cain, C. E. New York : Van 

 Nostrand. Pp. 118. Price, 50 cents. 



The Foes of the Farmers. By A. L. 

 Perry. Nebraska Board of Agriculture. 

 Pp. 20. 



Missouri Iron-Ores. By Adolf Schmidt, 

 Ph. D. Jefferson City, Mo. : Regan & Car- 

 ter. Pp. 16. 



Climate of the Glacial Period. By Thos. 

 Belt, F. G. S. Pp. 44. 



Habits of Some American Species of 

 Birds. By Thomas G. Gentry. Pp. 16. 



Researches in Acoustics. Paper V. By 

 Alfred M. Mayer. Pp. 42. 



Drift of Medical Philosophy. By D. A. 

 Gorton, M D. Philadelphia : Lippincott & 

 Co. Pp. 70. 



Supplement to the Calculus of Opera- 

 tions. By John Patterson, A. M. Pp. 8. 



Longevity of Brain-Workers. By Geo. 

 M. Beard, M. D. Pp. 16. 



National Teachers' Monthly. New York : 

 Barnes & Co. One dollar per year. 



Legal Relations of Emotional Insanity. 

 By E. Lloyd Howard, M. D. Pp. 12. 



The Analyst : Journal of Pure and Ap- 

 plied Mathematics. Des Moines, Iowa. Two 

 dollars per year (bi-monthlyl. 



MISCELLANY. 



Climate of the Glacial Period. This 



subject is discussed, in the October number 

 of the Quarterly Journal of Science, by Mr. 

 Thomas Belt. The cold of the glacial 

 epoch, he thinks, was caused neither by 

 elevation of the land in high latitudes, nor 

 by the position of the earth due to the ec- 

 centricity of its orbit, as suggested by Ly- 

 ell, Croll, and others ; but rather by great 

 obliquity of the ecliptic. If the axis of our 

 globe be as that of Jupiter, the days and 

 nights would be twelve hours each, and 

 there would be no succession of seasons. 

 The hot climate of the equator would be- 

 come more temperate toward the poles, 

 and no snow could accumulate at the sea- 

 level, except, perhaps, immediately around 

 the poles. 



With beginning of obliquity of the sun's 

 path, seasons of heat and cold would suc- 

 ceed each other, and these would become 

 respectively lengthened and intensified as 

 the obliquity increased. The long winters 

 of intense cold would cause great accumu- 

 lation of snow, which the summer could 

 not melt. A climate is made more severe 

 by presence of ice and snow, as many of 

 the sun's rays of both heat and light are 

 reflected, and the earth is not warmed by 

 them. Thus, whatever tends to increase 

 the area of snow increases the severity of 

 the climate. The growth of the ice-sheet 

 would cause it to extend toward the equa- 

 tor, and the movement of warm currents 

 might be arrested. The heat of their waters, 

 before expended in melting ice in the polar 

 regions, would now produce great evapora- 

 tion along the margin of the ice-belts, and 

 the source of rainfall be augmented. 



The great obliquity of the sun's path, 

 contended for by Mr. Belt, exists in the 

 planet Venus, where the tropics overlap 

 the polar circle, and a similar state of 

 things here would give us the glaciers as 

 they existed in the ice-age. Moreover, a 

 change in its obliquity back until the sun's 

 path was over the equator, would give the 

 climate which produced tropical plants 

 within the polar circle. The fact of their 

 existence demonstrates the presence there 

 of a mild climate as enormous unmelting 



