SCIENCE. 



Editoeial Committee : S. Newcomb, Mathematics ; R. S. WooDWARn, Jlechanics ; E. C. Pickebing, As- 

 tronomy ; T. C. Mendenhall, Physics ; R. H. Thurston, Engineering ; Iea Remsen, Chemistry ; 

 Joseph Le Conte, Geology; W. M. Davis, Physiography; O. C. Marsh, Paleontology; W. K. 

 Brooks, Invertebrate Zoology ; C. Haet SIerriam, Vertebrate Zoology ; N. L. Britton, 

 Botany ; Hexry F. Osboen, General Biology ; H. P. Bowditch, Physiology ; 

 J. S. Billings, Hygiene ; J. McKeen Cattell, Psychology ; 

 Dasiel G. Brixton, J. W. Powell, Anthropology. 



Friday, May 17, 1895. 



CONTEXTS: 



The Ballistic Galvanometer anil its use in Magnetic 

 Measurements : Thosias Gray 533 



The Scientific Method and Modern Intellectual Life : 

 Conway MacMillax 537 



The Liquefaction of Gases — A Controversy : Ja JIES 

 Lewis Howe 542 



Current Xotes on Anthropology ( VIIL ) : D. G. 

 Brinton 544 



James Edward Oliver: George Bruce Halsted. .544 



James Dnight Dana 545 



Correspondence : — 546 



The Education of the Topographer: W. M. 

 Davis. The Uclmholtz Memorial : Hugo MiJN- 

 sterbeeg. 



Scientific Literature: — 548 



Dana's Geology: Joseph Le Conte. Warm- 

 ing's Systematic Botany; Chambers' Story of the 

 Stars: DavidP. Todd. Ballard's T!ie World of 

 Matter: Wyatt W. RANDALL. 



Notes and Xews 554 



Societies and Academies : — 558 



The Geological Society of Washington ; The En- 

 tomological Society of Washington. 



New Books 560 



MSS. intended for publication and books, etc., intended 

 for review stiould be sent to the responsible editor, Prof. J. 

 McKeen Cattell. Garrison on Hudson, N. Y. 



Subscriptionsand advertisements should be sent to Science, 

 41 N. Queen .St., Lancaster, Fa., or 41 East 49th St., New York. 



THE BALLISTIC GALVANOMETER AND ITS 

 USE IN MAGNETIC MEASUREMENTS. 

 The ballistic g-alvanometer gives one of 

 the most convenient and reliable means of 

 measuring the total quantity of electricity 

 conveyed through a circuit by a transient 

 current when the conditions are such as to 

 atlmit of its legitimate application. It is 

 well known, however, to experienced ob- 



servers that in a large number of the com- 

 mon applications of the instrument the re- 

 sults are doubtful because the fundamental 

 principle on which the calculations are based 

 is not sufficientlj^ attended to. The object 

 of the present note is to direct more par- 

 ticular attention to the conditions under 

 which accurate results may be obtained. 



Most text-books on electrical measure- 

 ments give formuliB for the calculation of the 

 quantity of electricity required to produce 

 a given deflection, or throw, of the galva- 

 nometer needle, and also indicate how the 

 constant of the instrument may be de- 

 termined, and how the damping effiect of 

 the air and of induced currents may be al- 

 lowed for. The formultc assume as fimda- 

 mental that the duration of the flow is 

 negligibly small in comparison with the 

 time which the needle takes to reach its 

 greatest deflection. This fundamental con- 

 dition is of course implied in the name bal- 

 listic, but it does not seem, from the appli- 

 cations which we find continuallj' made of 

 the instrument, that the simple statement, 

 as commonly given, is suflicientlj- explicit 

 to prevent a vicious use of this method of 

 experiment. For the measurement and the 

 comparison of the capacities of condensers 

 and similar purposes the ballistic galva- 

 nometer is generally reliable, providing the 

 constant is properly determined and suit- 

 able appliances used for manipulation. In 

 magnetic measurements, however, it not 



