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the more advanced stages of society, the two kinds of exertion 

 are made by different minds. One set of men take to the arts, 

 another to the sciences. They both labor for a common end. 

 They are each dependent on the other. The philosopher must 

 have instruments of research which only the artificer can make, 

 and the artificer, facts and principles, which only the philoso- 

 pher can furnish. Each art is dependent, in fact, not on one 

 science only, but on many sciences, and each science contrib- 

 utes aid to, and receives aid from, many different arts. In 

 general, the arts and their related sciences keep step together 

 navigation, with astronomy mi 11- work and manufactures with 

 mechanical science. And conversely, the sciences can only 

 advance with the arts that supply their instruments and appa- 

 ratus of research. Chemistry must needs have her blowpipes 

 and furnaces, her crucibles, retorts and balances ; and astron- 

 omy, her telescope, circle and clock. Physiology, animal and 

 vegetable, is blind without the microscope. And even the 

 mathematics, so preeminently abstract and dissociated from 

 material things, can yet stoop to the use of mechanism, and 

 grind out numerical results, like coffee, from a species of mill 

 turned by a crank the calculating engine. 



While the sciences, then, freely acknowledge their obliga- 

 tions to the arts, let the arts, also, give due credit to the 

 sciences. The true relation between them, as we have seen, is 

 that of co-workers for a common end ; co-partners, if you 

 please, in the great business of advancing the welfare of man. 

 Science does her part of the work, we may say, chiefly in the 

 office ; art, hers chiefly in the shop. Science furnishes the 

 brain, art the brawn. And the greater, and more difficult, 

 and more exacting the work, the greater the need of sound 

 theory at the desk, as well as sound practice at the bench of 

 science, as well as skill and energy, for the perfection of indus- 



