348 



SCIENTIFIC THOUGHT. 



27. sidering nature a great impetus. As we have seen, it 



The astro- 



vew ical was en tirely an outcome of Newton's great discovery. 

 mota- ic and ^ * s sometimes useful to distinguish between cosmical, 

 phenomena, molar, and molecular phenomena ; it is, however, well to 

 note that this distinction is a popular or practical, not a 

 scientific one. The question, in how far pure magnitude 

 affects the appearance and relations of the parts or ele- 

 ments of which the universe is composed, is indeed of 

 great scientific interest, but it has not yet received a 

 definite answer. In the meantime we can use the term 

 cosmical for such magnitudes of space, mass, or time as 

 far transcend our own powers of direct measurement by 

 the foot-rule, the balance, and the timepiece, and still 

 more, our powers of direct action : those dimensions com- 

 pared with which our own homes and actions absolutely 

 disappear. "We will call molar those masses which we 

 can handle directly, those dimensions in which we build 

 our own homes and pass our own lives. And we will 

 call molecular those sizes and masses which on the other 

 side are so small that the utmost powers of the micro- 

 scope and the dividing machine fail to make them directly 

 visible, still less tangible or manageable for our active 

 powers. The lines which limit these three regions are 

 indeed neither fixed nor fixable ; the middle region, which 



mathematics, and his knowledge of 

 astronomy was mainly derived from 

 books. . . . Thus Faraday was de- 

 barred -from following the course 

 of thought which had led to the 

 achievements of the French philo- 

 sophers, and was obliged to explain 

 the phenomena to himself by means 

 of a symbolism which he could un- 

 derstand, instead of adopting what 

 had hitherto been the only tongue 



of the learned " (Clerk Maxwell, 

 "Action at a Distance," 'Proceed- 

 ings of the Royal Institution,' vol. 

 vii. Reprinted in ' Scientific Papers, ' 

 Cambridge, 1890, vol. ii. p. 317 sq. 

 Cf. also vol. i. p. 156). Du Bois- 

 Reymond uses the term " astro- 

 nomical knowledge " in a somewhat 

 wider sense in his discourse " Ueber 

 die Grenzen des Naturerkennens " 

 (' Reden,' vol. i. p. 120). 



