LE ROY C. COOLEY. 37 



time as represented by the sun ; who catalogued the 

 stars, discovered the precession of the equinoxes, calcu- 

 lated longitude by means of eclipses: who, in a word. 

 left, at his death, the mass of astronomical facts which 

 were afterwards elaborated by Ptolemy into a theory of 

 the solar system. 



Now the instrumental method was the chiefest ele- 

 ment in this wonderful progress from Thales to Hip- 

 parchus. An invention is to science, sometimes, what 

 the relay is to the telegraphic message. When the im- 

 petus of the past is nearly exhausted a new instrument 

 lets in a fresh energy to impel it further. So the inven- 

 tion of the telescope was the starting point of modern as- 

 tronomy ; and so the invention of the spectroscope was 

 the opening of the gateway into celestial chemistry. 



Scarcely can an original research be conducted in 

 modern science without the aid of mechanical invention. 

 New lines of thought exhaust the capacity of old instru- 

 ments, and discovery then pauses until new ones are made: 

 as when Crookes, investigating high vacua, reached the 

 limit of all the old appliances for exhausting air while 

 he was yet upon the very threshold of his problem, and 

 could go no further until he devised mechanical im- 

 provements in his air pump. The invention of the in- 

 strument is a step in the investigation as truly as is the 

 discovery of facts by the use of it or the induction based 

 upon the facts discovered. 



Even in sciences which depend least upon the use of 

 instruments, the faculty of invention is in constant req- 

 uisition. Invention consists in combining old elements 

 into new forms adapted to supply a want or to fulfill a 

 purpose. But this definition will apply to thoughts as 

 well as to bodies of matter. A rearrangement of old 

 thoughts to form a new one, is as truly an invention as 

 the rearrangement of known mechanical principles to 



produce a new device. A new arrangement of bodies 



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