■ *'2 Scientific Intelligence. 



knowledge in those branches of Terrestrial Magnetism with which 

 it deals, but is intended to give a connected account of my own 

 original work in that subject, referring to the work of others only 

 so far as is necessary for intelligibility." Some of the subjects 

 dealt with are the following : — magnetic records, secular and non- 

 cyclic changes, diurnal inequalities, annual variations, comparison 

 of arctic and antarctic disturbances, sunspots and terrestrial mag- 

 netism, etc. h. s. u. 



8. A Physical Study of the Firefly; by William W. Coblentz. 

 Pp. 47, with 14 figures and 1 plate. Washington, 1912 (Publi- 

 cation No. 164 of the Carnegie Institution of Washington). — This 

 paper gives the l'esults obtained by a systematic investigation, 

 extending over a period of about four years, of the light emitted 

 by various organisms, especially by the fireflies Photinus pyralis 

 and Photuris pennsylvanica. Careful and accurate determina- 

 tions have been made of the spectral energy curves of the light 

 emitted by fireflies, of the luminous efficiency and candle-power, 

 of the radiations and temperature, and of the infra-red absorp- 

 tion. The spectrograms reproduced on the plate are clear-cut, 

 and the whole subject is presented in a thorough and interesting 

 manner. At the end of the paper may be found a bibliographical 

 list of the most important articles bearing on the subject. 



h. s. u. 



9. Elements of Hydrostatics ; by George W. Parker. Pp. 

 viii, 150, with 48 figures. London, 1912 (Longmans, Green & 

 Co.). — This book is intended to be a sequel to the author's "Ele- 

 ments of Mechanics." The treatment is very elementary, and 

 presupposes only an acquaintance with algebra, geometry, and a 

 few fundamental principles of mechanics. Numerous illustrative 

 problems are worked out in the text, and 204 examples for solu- 

 tion by the student are collected in 16 sets. The answers to these 

 original problems are given at the end of the volume. The author 

 lays stress on the importance of solving problems directly from 

 basic principles, and discountenances the substitution of numerical 

 data in algebraic formulae, whenever this process can be reason- 

 ably avoided. h. s. it. 



II. Geology and Natural History. 



1. The Effect, of Topography and Isostatic Compensation 

 upon the Intensity of Gravity ; by John T. Hayford and 

 William Bowie. U. S. Coast and Geodetic Survey. Pp. 132 ; 

 19 illustrations. Washington, D. C, 1912. — It has long been 

 known that the larger topographic provinces of the earth's surface 

 hold their different vertical relations because of different densities 

 in the subcrust, the solid crust thus resting in equilibrium; but it 

 remained for Hayford to show that the relation was very close, 

 areas as small as ten thousand square miles commonly having 

 their mean elevation as much as nine-tenths compensated. He 



