562 



SCIENCE 



[N. S. Vol. XXXVII. No. 954 



the labels by rubbing the surface in a moist- 

 ened groove in a cake of sapolio. 



A. F. Blakeslee 

 Carnegie Station for 

 Experimental Evolution, 

 Cold Spring Harbor, N. Y. 



most is — what? 

 To THE Editor of Science: Since tbe nat- 

 ural sciences came into their inheritance, 

 about thirty years ago, it has been quite the 

 orthodox thing with the " humanists " to 

 demonstrate the inherent disability of these 

 subjects to impart " culture " by satirically 

 deriding the English of embryonic doctorial 

 dissertations. Judge, therefore, of the shock 

 to my esthetic sensibilities occasioned by 

 this sentence, which stands on page 61 

 in the issue of Science for January 10: 

 " most of the brotherhood of teachers of Eng- 

 lish is in the same state" where the adjective- 

 noun most, having the plural form because 

 clearly referring to number and not quantity, 

 is made the subject of a verb in the singular 

 number. This communication appears to have 

 been written by a professor of English and, 

 presumably, a humanist. 



F. W. Martin 



SCIENTIFIC BOOKS 

 Methods of Measuring Electrical Resistance. 



By Edwin F. Noethrup, Ph.D. New York, 



McGraw-Hill Book Company. 1912. Pp. 



xiii-f 389. Price $4.00. 



The measurement of electrical resistance is 

 of interest not only to the physicists but to 

 engineers and others engaged in scientific, 

 technical and commercial work. The methods 

 used are described in various technical and 

 scientific papers and in text-books on electrical 

 measurements. But only a few of these are 

 described in any one place, if we except Price's 

 book written about twenty years ago. The 

 author " has selected for presentation all 

 those methods which in his judgment are use- 

 ful, for commercial tests and measurements, 

 for purposes of instruction in educational in- 

 stitutions and for application in technical and 

 research laboratories." So we have collected 



in one book a large number of methods cov- 

 ering practically the entire field of electrical 

 resistance measurements. 



The first part of the book is of an intro- 

 ductory character and better than any other 

 shows the wide experience and sound judg- 

 ment of the author in matters pertaining to 

 electrical measurements. Particularly good 

 are his comments on accuracy and method and 

 few there are, of those who make electrical 

 measurements, who could not read with profit 

 the first six pages. Then follows a discussion 

 of errors and estimation of the accuracy ob- 

 tainable by deflection methods. The way an 

 error in measurement may affect the result 

 desired is clearly shown, but no effort is made 

 to arrive at the probable accuracy by the 

 means of the theory of probabilities. 



Deflection methods are taken up first. Va- 

 rious voltmeter methods and voltmeter and 

 ammeter methods are considered very fully. 

 Then follows a discussion of null methods and 

 of these the differential galvanometer meth- 

 ods are considered first. In this connection 

 no mention is made of the Kohlrausch method, 

 which is generally considered to be by far the 

 best and by some to be the only differential 

 galvanometer method suitable for use in the 

 precise comparison of resistances. 



In the discussion of the Wheatstone bridge 

 methods the Carey Foster method receives the 

 fullest consideration. Six kinds of measure- 

 ments are listed for which it is stated that 

 this method " is especially useful." For one 

 of these measurements deflection methods 

 give all that is usually desired. When a 

 higher accuracy is necessary it is easily ob- 

 tained by the simplest kind of a bridge. 

 Another is of interest only to the manufac- 

 turer in the adjustment of resistance coils. 

 The other four can, provided a substitution 

 method is used, be made much better with a 

 simple bridge costing not more than half as 

 much as the Carey Foster bridge. 



In the discussion concerning Wheatstone 

 bridges various arrangements of ratio and 

 rheostat coils, including the author's four-coil 

 decade, are considered; the author's special 

 bridge for reading directly the per cent, error 



