468 



SCIENCE. 



[N. S. Vol. XI. No. 273- 



ent8 ; the mean heights of clouds from different 

 directions ; the mean velocities and frequencies 

 of the clouds at different heights ; the frequen- 

 cies of the different currents at different heights, 

 etc. The mere enumeration of the headings of 

 these tables will suffice to show the thorough- 

 ness of the work discussed in this volume — a 

 thoroughness which is characteristic of all of 

 Mr. Clayton's cloud studies. The text accom- 

 panying the tables discusses the methods of 

 measurement and of computation employed, 

 and the meteorological results of the investiga- 

 tion. It is impossible to present any adequate 

 summary of the Important results reached by 

 Mr. Clayton. Those who seek further informa- 

 tion should turn to the volume itself, which is 

 worthy of careful study. There is, however, 

 one point which we would notice here. From 

 a series of special measurements of cumulus 

 and fracto-cumulus clouds, made with a view to 

 determining the relation between the heights of 

 these clouds as obtained by theodolites and 

 from the dew-point, it appears that turreted 

 cumulus clouds are most frequent at the coldest 

 time of day, and not at the warmest, as is the 

 case with ordinary cumulus. Thus, as Mr. 

 Clayton points out, it seems that the diurnal 

 period of the turreted cumulus is not deter- 

 mined by heating at the ground but by cooling 

 at the surface of the cloud. The turreted cumu- 

 lus probably forms only when the decrease of 

 temperature from other causes approaches the 

 adiabatic rate. It is thus an indication of 

 thunderstorms, for a rapid vertical decrease of 

 temperature in the upper air, wheu combined 

 with a rapid decrease in the lower air caused 

 by heating at the ground, favors the ascent of 

 columns of air from the ground, to great 

 heights and this is a condition favorable to 

 thunderstorms. 



The present volume is fully worthy to take 

 its place in the line of Blue Hill Observatory 

 publications as another important American 

 contribution to meteorology. 



E. DeC. Ward. 



BOOKS EECKIVED. 



Text-Booh of Paleontology. Kael A. VON Zittel. 

 Translated and edited by Charles E. Eastman. 

 London and New York, The Maomillan Company, 

 1900. Pp. ix -f 706. 



Volumetric Analysis. JOHN B. COPPOCK. London, 

 Whittaker & Co. ; New York, The Macmillan 

 Company. 1900. Pp. 92. 



The Soul of Man. Paul Caeus. Chicago, The Open 

 Court Publishing Company. 1900. Pp. xviii-|-482. 



The Teaching of Elementary Mathemaiics. DAVID 

 Eugene Smith. New York and London, The 

 Maomillan Company. 1900. Pp. xv + 312. 



The Criminal, his Personnel and Environment, a scien- 

 tific study. August Deahms, with an Introduc- 

 tion by Cesare Lombeoso. New York and Lon- 

 don, The Macmillan Company. 1900. Pp. xiv-f40. 



SOCIETIES AND ACADEMIES- 

 IB.^ PHILOSOPHICAL SOCIETY OF WASHINGTON. 



At the 514th meeting of the Society, held at 

 the Cosmos Club on March 3d, Professor C. 

 Abbe read an obituary notice of Professor H. 

 A. Hazen. Dr. L. A. Bauer, then gave a de- 

 tailed statement of the methods to be pursued 

 in carrying out the magnetic survey of the 

 United States by the Division of Terrestial 

 Magnetism of the U. S. Coast and Geodetic 

 Survey. 



As an indication of the scope and character of 

 the data to be derived from the detailed mag- 

 netic survey of the United States, a brief state- 

 ment was given regarding the results obtained 

 from the detailed magnetic surveys of Mary- 

 land and of North Carolina. Furthermore 

 there were exhibited various charts giving a 

 graphical analysis of the earth's magnetic field 

 for various portions of the United States. 



With the aid of these charts, it was shown 

 very clearly how inadequate it is for the for- 

 mation of theories of the earth's magnetism to 

 have simply declination data alone. 



Following Dr. Bauer's paper. Dr. Alexander 

 Macfarlane of Lehigh University, discussed the 

 'Square Root of minus one.' He reviewed the 

 explanations published by Payfair, Bu6c, Ar- 

 gaud, Frangais, Gauss, Cauchy, Boole, Hamil- 

 ton, Cayley and other mathematicians and 

 concluded that V — 1 does not indicate direc- 

 tion nor rotation of the quantity to which it is 

 attached, nor a turning of the plane of repre- 

 sentation, nor a special unit ; that + and- — are 

 not signs of addition and subtraction but are 

 signs of affection, and so is j/ — 1. He gave 

 analytical expressions for these signs, which 



