[From the Kensington Museum Handbook, pp. 1 21.] 



LXXVIII. General considerations concerning Scientific Apparatus. 



1. EXPERIMENTS. 



THE aim of Physical Science is to observe and interpret natural phenomena. 



Of natural phenomena, some as, for example, those of astronomy are not 

 subject to our control, and in the study of these we can make use only of 

 the method of Observation. When, however, we can cause the phenomenon to 

 be repeated under various conditions, we are in possession of a much more 

 powerful method of investigation that of Experiment. 



An Experiment, like every other event which takes place, is a natural 

 phenomenon ; but in a Scientific Experiment the circumstances are so arranged 

 that the relations between a particular set of phenomena may be studied to 

 the best advantage. 



In designing an Experiment the agents and phenomena to be studied are 

 marked off from all others and regarded as the Field of Investigation. All 

 agents and phenomena not included within this field are called Disturbing 

 Agents, and their effects Disturbances ; and the experiment must be so arranged 

 that the effects of these disturbing agents on the phenomena to be investigated 

 shall be as small as possible. 



We may afterwards change the field of our investigation, and include 

 within it those phenomena which in our former investigation we regarded as 

 disturbances. The experiments must now be designed so as to bring into 

 prominence the phenomena which we formerly tried to get rid of. When we 

 have in this way ascertained the laws of the disturbances, we shall be better 

 prepared to make a more thorough investigation of what we began by regarding 

 as the principal phenomena. 



VOL. II. 64 



