ME THOD OF DISCO V BRING CA VSAL LAWS 197 



The use of the method of residues as a &quot;finger-post to the un 

 explained&quot; by the study of residual phenomena, has proved most 

 fruitful in scientific research, and deserves particular attention. 

 Applied in this way, it is obviously a method of discovery rather 

 than of proof, a source of hypotheses rather than a means of test 

 ing them. In sciences like astronomy and chemistry, where exact 

 calculations and measurements are extensively employed, very 

 remarkable discoveries have been made by the application of it. 



&quot; Almost all the greatest discoveries in astronomy,&quot; writes Sir 

 John Herschel, 1 &quot; have resulted from the consideration of residual 

 phenomena of a quantitative or numerical kind.&quot; The discovery 

 of the planet Neptune by Adams and Leverrier in 1846 is a 

 striking example. By calculating the effects of all known attrac 

 tions on the planet Uranus, the path of the latter in the heavens 

 was determined. This planet was actually found, however, to be 

 sometimes before and sometimes behind the place calculated for 

 it. It was concluded that the discrepancy, the &quot; residual effect,&quot; 

 must be due to the attractive influence of some unknown heavenly 

 body. The search for this latter resulted in the discovery of 

 a hitherto unknown planet Neptune. 



In the domain of chemistry, we may instance the discovery, 

 by Lord Rayleigh and Professor Ramsay, in 1894, of a chemical 

 element, which they called argon, present in the atmosphere in 

 very minute quantities. &quot;The investigation started from the 

 detection of an unexplained residual phenomenon. Careful de 

 termination of density had shown that nitrogen obtained from 

 various chemical compounds is of a uniform density, but that 

 atmospheric nitrogen is about \ per cent, heavier&quot;. 2 In ex 

 planation of this residual phenomenon numerous hypotheses were 

 advanced, and a long series of experiments culminated in the 

 discovery of the new chemical element. 



245. SCOPE OF THE &quot; METHODS &quot;: USE OF SYMBOLS. The 

 various modes of procedure that have been outlined under the 

 title of &quot; methods,&quot; are simply applications of various grounds of 

 elimination, whereby we exclude irrelevant elements until the 

 causal connexion alone is left. They presuppose the dividing up 

 of our domain of inquiry into distinct factors, when mapping out 

 the field for possible hypotheses and forming the disjunctive judg 

 ment among the alternatives of which we hope to find the cause : 

 &quot; x is caused by either a, or b t or c, or . . ., or m &quot; (212). They 



l apud MELLONE, op. cit., p. 316. 2 C/. WELTON, op. cit., pp. 133-40. 



