May 26, 1916] 



SCIENCE 



743 



breeder in cotton investigations at the Texas 

 Station, and has been succeeded by Rupert L. 

 Stewart. 



Dr. F. J. E. WooDBRiDGE, Johnsonian pro- 

 fessor of philosophy in Columbia University 

 and dean of the graduate faculties, has been 

 appointed lecturer in philosophy on the Mills 

 Foundation in the University of California, 

 from January 31 to June 30, 191Y. 



Dr. William F. Allen, instructor in anat- 

 omy. University of Minnesota, has accepted a 

 position as professor of anatomy in the med- 

 ical department of the University of Oregon. 



Dr. Alfred L. Gray, professor of physiology 

 in the University of Virginia, has been trans- 

 ferred to the chair of roentgenology and has 

 been succeeded by Dr. Charles H. Lewis. 



Professor W. H. Twenhofel, of the Uni- 

 versity of Kansas, has been appointed asso- 

 ciate professor of geology at the University of 

 Wisconsin, to succeed Professor Eliot Black- 

 welder. 



Frank H. Probert, a graduate of the Royal 

 School of Mines, London, and for the past 

 twenty years engaged in consulting mining 

 engineering practise, has been appointed pro- 

 fessor of mining in the University of Cali- 

 fornia, as successor to the late Professor 

 Samuel Benedict Christy. 



Dr. Jean Felix Piccaed, of the University 

 of Lausanne, Switzerland, has accepted an 

 invitation of the University of Chicago to 

 spend next year at the university as assistant 

 professor of organic chemistry. Dr. Piccard, 

 who has worked with Professor Willstaetter 

 and been research assistant of Professor v. 

 Baeyer, will devote himself exclusively to 

 graduate work and to directing research in 

 organic chemistry. 



DISCUSSION AND CORRESPONDENCE 



CONSERVATIO VIRIUM VIVAEUM 



To THE Editor of Science : The term energy 

 was introduced by Thomas Young in 1807 to 

 denote MV^, or twice what is now known as 

 kinetic energy. Rankine extended its use to 

 cover potential and total energy. But though 

 the name was new the concept was not. This 

 was known long before under the term facultas 



agendi, which is in some respects more appro- 

 priate, for if our word energy is to be trans- 

 lated into Greek it must be rendered Sipa/xit 

 not ey^pyeia. 



The following extract from an old paper 

 contains a part of the early history of the idea 

 of energy.^ 



There seems to be a general impression that 

 the natural philosophers of the last century, 

 when they used the quantities now known as 

 kinetic, potential and total energy at all, re- 

 garded them from a purely algebraical or 

 geometrical point of view, failing to perceive 

 their great physical significance. In this re- 

 spect these physicists seem to have been under- 

 rated: as some passages from the first John 

 Bernoulli, Euler's teacher and D. Bernoulli's 

 father, will show. In a paper on the true con- 

 ception of living forces- he generalizes the 

 idea of vis viva and defines it as equivalent to 

 capacity for doing work, or facultas agendi, 

 which is simply a Latin equivalent of the 

 Greek energy [as Young understood it]. In 

 Section I. of this paper he says (translated) : 



Vis viva does not consist in the actual exertion, 

 but in the capacity for doing work; for it sub- 

 sists even when it does no work nor has any ob- 

 ject whereon it could act; so for example a 

 strained spring, or again a body in motion, has in 

 itself the capacity of doing work, so that if noth- 

 ing external to itself comes in its way upon which 

 it may exert itself, and so long as there is no ob- 

 ject present with which it can come in contact, it 

 infallibly retains it all undiminished by time, and 

 does not do the work which it would be capable 

 of doing if it had the opportunity. 



This seems a clear and even a vivid state- 

 ment of the law: 



When a system is subjected to no external 

 forces, its energy remains constant. 



In Section III. he takes a further step. 



Vis viva (which would be more aptly named fa- 

 cultas agendi, gallieS le pouvoir)3 is something real 



^Amer. Jour. ScL, Vol. 45, 1893, p. 97. See 

 also idem., Vol. 46, 1893, p. 151. 



2 " De vera notione virium vivarum, ' ' Acta 

 Eruditorium, Leipzig, 1735, p. 210. 



3 The term power is now rarely used for energy, 

 but it is scarcely a generation since this meaning 

 was common enough. Saint-Venant (op. cit., p. 



