MODE OF CONDUCTING AN ORIGINAL RESEARCH. 381 



on, until we have individually isolated each of the ele- 

 mentary bodies present in the original substance, and can 

 subdivide them in that manner no further. We then as- 

 certain if the sum of the weights of the elementary sub- 

 stances found exactly equals that of the original body. If 

 it does, the analysis is complete ; but if it does not, we 

 have either omitted some substance present, introduced 

 a foreign body, or committed an error of manipulation, 

 observation, or calculation; and we proceed at once to 

 correct the mistake. 



In the examination of a physical phenomenon, we pro- 

 ceed in a substantially similar manner, i.e., we divide the 

 conditions of it in every possible way, and into the smallest 

 distinct elements, and examine each portion, not only in a 

 qualitative manner, but also quantitatively, as far as the 

 circumstances of the case will admit. The quantitative 

 analysis of a physical phenomenon, however, can often be 

 only incompletely performed. In the analysis of such a 

 phenomenon, instead of dividing its conditions first into 

 groups, and then each group into its individual distinct 

 elements, as in chemical analysis, we usually separate one 

 only of its conditions at a time, leaving each time all the 

 remaining ones together ; and we then sometimes reduce the 

 complexity of the phenomenon by an element at a time, 

 or subdivide the phenomenon in other ways, according to 

 the circumstances of the particular case. In every case, 

 however, we reduce the phenomenon to its purest and 

 simplest state, by separating from it all its unnecessary 

 conditions, as soon as we can, in order to fit it for the 

 actual analysis. 



