July 28, 1916] 



SCIENCE 



135 



Bryan I 1 



We are thus led to the conclusion that under any 

 given conditions only a limited portion of the 

 energy of a system can be converted into mechan- 

 ical work. This portion is called the available 

 energy of the system subject to the given condi- 

 tions. In order, however, to completely define 

 the available energy of a system, it is necessary 

 to specify not only the external conditions to 

 which the system is subject, but also the means 

 at our disposal for converting energy into useful 

 work. 



Nernst : 2 



If any system whatever is subjected to any de- 

 sired changes, these are, in general, identified with 

 the following changes in energy: firstly, a cer- 

 tain amount of heat is either absorbed or given 

 out; secondly, a certain amount of external work 

 is either performed by the system or is performed 

 against it; thirdly, the internal energy of the 

 system will either diminish or increase. In gen- 

 eral in any event the diminution of the internal 

 energy V must be equal to the external work A ac- 

 complished by the system, minus the amount of 

 heat Q absorbed; i. e., the following relation ex- 

 ists: 



U = A — Q. 



Rushmore : 3 



From a practical standpoint energy may be 

 classified as available energy, or that which can 

 be turned into mechanical energy, and unavailable 

 energy, or that which is practically useless for the 

 purpose. To the latter belong the enormous 

 sources of energy stored in the earth's rotation, 

 as well as the interior heat of the earth. 



There are several reasons why we shall never 

 return to any former conception of the term 

 " energy " as Dr. Kent in his last paragraph 

 hints might yet be done. 



Every new study of the relationships only 

 strengthens the division as made above in the 

 three quotations. This view has been ex- 

 pounded so long and widely and is so firmly 

 established in all collegiate education that 

 there is slight excuse for combating it. It is 

 true that investigation and deduction increase 

 our knowledge of energy without disclosing 

 any ultimate interpretation, exactly as in the 



1 " Thermodynamics, " p. 35, 1907. 



- ' ' Theoretical Chemistry, ' ' trans, of sixth Ger- 

 man text, p. 8, 1911. 



s General Electric Review, p. 422, May, 1916. 



case of gravitation, yet the laws of transfer 

 and transformation are always found to hold 

 most rigidly. These laws of the conservation 

 of energy and the degradation of energy are 

 ever becoming more valuable and firmly estab- 

 lished. 



Recent discoveries and conceptions only 

 render a definition or unqualified statement 

 of what energy is more and more difficult. 



The development of radioactivity has enor- 

 mously broadened our field of knowledge on 

 energy and set us irrevocably beyond our past. 

 We find " energy " and " matter " meeting on 

 common ground and know not which from 

 t'other. 



The development of quantum theory and the 

 study of radiations again shatter any previous 

 notion of energy and portend that energy ideas 

 of the future must involve some aspect of 

 granularity and distribution function. 



All the studies on the constitution of matter 

 and the structure of atoms presage radical 

 change and new methods ; in dealing with whole 

 classes of energy we are finding the limits of 

 the application of the gross laws of energetics. 

 It is highly significant to follow the mathe- 

 matical physicist who with much pains in logic 

 comes inevitably to the conclusion that the 

 ether has infinite energy — a conclusion he will 

 likely abruptly discard as absurd! 



"With matter, ether and energy as possibly 

 only different aspects of, or approaches to, the 

 same ultimatum, who can imagine that our 

 ideas will ever again fit into the long-discarded 

 and outgrown definition. 



Useful work may comprise the chief end of 

 the engineer's effort, but it can do him only 

 good to have ever present the concept that 

 relatively only a negligible part of our energy 

 universe concerns itself with such work. It 

 would certainly be a great misfortune to have 

 a statement about energy so terse as to deny 

 the greatest and most useful of our generaliza- 

 tions. H. B. Pulsifer 



Armour Institute of Technology 



"typus" and "type" in taxonomy 

 There is a general attempt among syste- 

 matic zoologists and botanists to limit the 

 words " type " and " typical " and their equiv- 



