NECESSITY OF MANIPULATIVE SKILL. 31 3 



to possess a stock of ordinary and rare chemicals of the 

 highest attainable degree of purity, as well as cruder ones 

 for commoner purposes. Kare minerals and the residues 

 of peculiar manufacturing processes, especially those ob- 

 tained in the working of rare substances, constitute a 

 valuable addition to the stock of an investigating chemist, 

 because new elementary bodies and the wide-spread exist- 

 ence of the rarer elements have not unfrequently been 

 discovered by examining such substances. 



CHAPTER XXXIII. 



NECESSITY OF MANIPULATIVE SKILL. 



NEXT in importance to the skilful use of a gifted mind in 

 research comes dexterous employment of the human hand. 

 To the mental qualifications of scientific knowledge, 

 imagination, and invention, it is almost indispensable to 

 add aptitude in mechanical matters, and cleverness in 

 experimental manipulation. Great manipulative ability 

 can be acquired only by long practice, which should be 

 commenced at an early age. Fondness for mechanical 

 pursuits in a child has often betokened skill in discovery. 

 Newton, when a youth, was clever in constructing mecha- 

 nical toys. In scientific study also, as in other ab?truse 

 meditations, the mind soon becomes exhausted by intense 

 thinking, but is usually relieved by preparing and making 

 experiments. Study and manipulation in physics and 

 chemistry go hand-in-hand, and in actual research they 

 often alternate ; from the results of an experiment just 

 made we draw new conclusions and infer additional hypo- 

 theses, and we then make other experiments to test them, 

 and so on. 



