ATOMS AND MOLECULES 19 



existence of that substance is borne towards attracting 

 masses by the same measure of force. Every atom of 

 nitrogen or oxygen in the atmosphere encompassing the 

 whole earth is drawn towards its centre to the same 

 extent. Atoms of sodium, if on the earth or in the sun, 

 in Sirius or distant Orion, or wherever in the universe 

 they exist, are true, each one to its kind, attract and are 

 attracted even as they. It is so with every element. 



It is, we say, indirectly that atoms can be weighed. 

 It is far from the power of man to separate atom from 

 atom, weigh the one against the other, and note the 

 perfection of their balance. It is far beyond his power 

 to devise and make a balance for an experiment so fine. 

 He cannot deal with single atoms. He lacks, even when 

 aided by the microscope, the perceptive power and the 

 refinement of touch capable of distinguishing, handling, 

 or in any way singling them out and acting on them. 

 And yet single atoms have been in some way dealt with, 

 handled, and acted on. Every particle has been weighed, 

 and weighed to a nicety, is of a weight that corresponds 

 with minutest exactness, with that of the countless par- 

 ticles of its kind. Never was balancing like it. The 

 greatly differing weights in the different kinds of atoms 

 so small, render more impressive the sameness in the 

 same element. What, then, hath weighed them with 

 such accuracy ? Where were the balances found ? What 

 possessed the power of using them in such a fashion? 

 What made all the atoms of hydrogen of one lightness ? 

 What made those of oxygen sixteen times heavier, those 

 of all the elements just their own numbers of times 

 heavier? Let a man produce before a company huge 

 scales of accuracy so exquisite that a grain of dust would 

 disturb the balance ; let him put into the one a mighty 

 mass of iron, into the other of copper ; let him vary the 



