282 



SCIENCE 



[N. S Vol. XLII. No. 1078 



part of the responsibility for the hopeless eon- 

 fusion which they allege exists regarding the 

 distinction between mass and weight. Their 

 own explanation of this matter however differs 

 from mine chiefly in the picturesqueness of the 

 language employed. I have, indeed, reeog- 

 nized^ that if full rigor is insisted on it is 

 necessary to make a distinction not mentioned 

 by Professors Franklin and MacNutt. The 

 word weight, according to scientific usage, does 

 not usually mean the actual " force with which 

 the earth puUs on a body," but something 

 which differs from this because of the earth's 

 rotation. I have not advocated introducing 

 this distinction in the first explanation of 

 weight to students; but it can not be perma- 

 nently avoided if any important attainment is 

 reached in the study of dynamics. 



Since the writers have referred to me in 

 connection with the meaning of the division 

 by g, I may say that I certainly am not one of 

 those who believe that weight is converted into 

 mass by dividing by g or by any other process. 

 I believe, however, that the fact should be made 

 clear that mass, like any other measurable 

 magnitude, is expressible in diilerent units; 

 and that the reduction from one unit to another 

 involves precisely the same kind of reasoning 

 in the case of mass as in the case of length or 

 velocity. One can not understand the reduc- 

 tion of a length from feet to meters unless he 

 understands the meaning of both the foot and 

 the meter; a similar statement holds concern- 

 ing the reduction of a mass from pounds to 

 tons, or f romi pounds to " slugs." Moreover, I 

 see no reason why the unit which has been 

 called the slug should be regarded with ridi- 

 cule, or even with semi-ridicule. The question 

 of what unit to employ for any given purpose 

 is properly decided by convenience. The con- 

 venience of the " slug " is due to two facts — 

 (1) that the pound-force is customarily em- 

 ployed in a great deal of practical work and (2) 

 that the dynamical formulas almost universally 

 used are based upon a relation of units such 

 that unit force acting upon unit mass causes 

 unit acceleration. And there should be no 

 more difficulty in understanding the definition 



2 Science, April 23, 1915, p. 611. 



of the " slug " than that of the dyne or the 

 " standard pound-force " or any other unit 

 which is defined by an appeal to the law of 

 acceleration. L. M. Hoskins 



QUOTATIONS 



BRITISH SCIENTIFIC MEN AND THE GOVERNMENT 



In addition to appointing committees to con- 

 sider suggestions or inventions, the Royal, 

 Chemical and Physical Societies have taken 

 steps to obtain registers of their fellows classi- 

 fied according to special knowledge and to 

 scientific services which the fellows are willing, 

 as well as specially qualified, to perform. The 

 idea in each case is to secure cooperation 

 among the fellows of the particular societies, 

 and to examine by means of committees any 

 promising suggestions relating to munitions 

 of war or kindred subjects. No one knows pre- 

 cisely what will be done with the registers 

 when they have been completed. Each society 

 seems to be compiling its list independently 

 and without any clear view of the use which 

 will be made of the experts' services which 

 will become available by the response to its 

 circular. No scheme has yet been put forward 

 by which definite national duties will be as- 

 signed to the hundreds of scientific men who 

 are enrolling themselves on the registers of 

 their respective societies. . . . 



The laboratories of our universities, univer- 

 sity colleges and technical institutions are at 

 the disposal of the government, and in many 

 of them men are devoting twelve hours a day 

 to work in connection with the supply of 

 munitions of war. A few days ago the mem- 

 bers of the Eoyal Institution decided to offer 

 the resources of their laboratories and of the 

 Davy Paraday Research Laboratory to the 

 government for the prosecution of any partic- 

 ular research by officers of the admiralty, war 

 office or ministry of munitions; and the man- 

 agers invited communication from these de- 

 partments " in case there is any field of re- 

 search in relation to or connected with chem- 

 ical and physical science, or either of them, to 

 which the professors, assistants and staff of the 

 Royal Institution or of the laboratory can use- 

 fully direct their attention with the view of 



