GENERAL CONSIDERATIONS 



CONCERNING 



SCIENTIFIC APPARATUS. 



i . EXPERIMENTS. 



THE aim of Physical Science is to observe and interpret natural 

 phenomena. 



Of natural phenomena, some as, for example, those of astro- 

 nomy are not subject to pur 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 circum- 

 stances 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 Disturb- 

 ances ; 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 investiga- 



B 



