426 ACTUAL WORKING IN ORIGINAL RESEARCH. 



can, after close scrutiny, be thus found, the case is a diffi- 

 cult one. Either scientific knowledge is not sufficiently 

 advanced to afford the true explanation, or the discovery 

 of it lies beyond our mental power ; or we have met with 

 a phenomenon of a new and unknown kind. 



If in any case, after all our test experiments and con- 

 clusions, the assumed cause is found not to be the true 

 one, we must imagine others and test them until the true 

 one is discovered ; and if we experience great difficulty in 

 finding it, we may then make radical changes or even 

 haphazard experiments. Such changes and experiments 

 may also be made when any inscrutable interference or 

 even too great harmony of effects occurs ; in the latter 

 case because such harmony is extremely suspicious, and 

 strongly indicates an uniform error. Any circumstance 

 also, no matter how small or apparently insignificant it 

 may be, which we meet with in a research, and which we 

 cannot at all reconcile with the other circumstances pre- 

 sent, or with the known principles of science, is always 

 worthy of the deepest study and investigation, because it 

 often contains the true explanation, or else an anomalous 

 and therefore important truth. 



A supposed cause should always be tested in as many 

 ways as possible, aud those conditions selected which yield 

 the most conclusive result. We should try (if we can) the 

 effect of presence, absence, direction, and quantity of each 

 condition. Previous to or whilst varying the conditions 

 of an experiment it is often of service to form a written 

 list of the chief variations which can be made, something 

 like the following, but much more fully, and more adapted 

 to the special case : Change the forces employed, con- 

 sidering each force in succession ; change the strength of 

 the forces ; vary their direction ; employ different sub- 

 stances, considering the probable effect of different classes 



