382 ACTUAL WORKING IN ORIGINAL RESEARCH. 



CHAPTER XL. 



ADVANTAGES OF VARIETY OF EXPERIMENTS. 



A VARIETY of well-devised experiments is of the highest 

 importance, and is much more likely to yield valuable 

 discoveries than any mere iiumber of similar ones, espe- 

 cially if the questions involved in the experiments are 

 some of them intrinsically momentous. It also supplies 

 us with results and data by means of which we can, by 

 processes of comparison and inference, determine the 

 causes, coincidences, and other abstruse relations of 

 phenomena. Variety of experiments is also the chief 

 means by which the indifferent and unessential circum- 

 stances, and those which interfere with a phenomenon we 

 are investigating in a new research, are quickly disclosed 

 and detected. If the conditions of an experiment are not 

 sufficiently varied, we can hardly be sure that unsuspected 

 influences have not affected the results; nor can we be 

 certain that our interpretation of the results is correct. 

 A uniform method of working may conceal a uniform 

 error. In every experiment there are always many ways 

 of failing, and usually only one way of succeeding ; and no 

 precise rule can be laid down, either for preventing errors 

 in experiments or for excluding those errors which have 

 been detected, because the methods of preventing or 

 excluding them differ somewhat in every different case. 

 Failure in experiments often arises from want of proper 

 materials, or proper proportions of them, and in a great 

 variety of other ways. ' Although the truth is not always 

 arrived at by the first experiment, that is not the case 

 because the first idea of the experiment is not very often 



