THE AIM AND ACHIEVEMENTS OF SCIENTIFIC METHOD. 91 



remark, made so long ago as 1867 by Rankine,* that " one of 

 the chief objects of mathematical physics is to ascertain, by 

 the help of experiment and observation, what physical 

 quantities are ' conserved.' " 



The illustration also brings out the fact that the con- 

 stancies established in such investigations tire of an entirely 

 conventional character and refer to nothing Objectively " trans- 

 ferred." We assumed that the two temperature changes were 

 different aspects of the same transaction, an assumption whose 

 consequences are made psychologically available by throwing it 

 into the form of a transfer of " heat." We correlated the 

 various terms of the series of temperatures and weights which 

 appear in this transaction with numbers. If our initial 

 assumption was correct, it seems now that some manipulation of 

 the data here the weights and temperature changes must 

 yield an equality, the particular form of this manipulation 

 depending upon the particular manner in which the number 

 series has been correlated with the series of objective states of 

 the body. Our success in finding the desired manipulation 

 implies that, in the language of Lotze/f the bodies *dp " take 

 note " of one another's changes of condition, " and that the 

 data We have manipulated, that is the original data with which 

 numbers were correlated, are the complete expression of that 

 " notice."- In short, it is the verification in a particular case of 

 the postulate of the rationality of the world. 



35. 



On the other hand, failure to find- this manipulation will 

 always prompt the investigator to look further afield to 

 discover other modifications of things which must be con- 

 sidered as elements, hitherto unrecognised, of the transaction 

 in question. Thus, to pursue our illustration a little further, 



* Quoted by Merz, op. tit., p. 140. See also Divers, in B.A. Report, 

 1902, pp. 557, et seq. 



t Lotze, Metaphysics (Eng. Trans.), i, 45, p. 118. 



