16 ORGANIC EVOLUTION CONSIDERED 



If we grind a piece of sulphur in a mortar, we 

 break it into smaller and smaller pieces, each of 

 which is sulphur. If we could put it into the mor- 

 tars of the gods, which, it is said, "grind slow but 

 exceeding small," would there be any practical 

 limit to the smallness of the pieces? Is there a limit 

 in the division of matter beyond which nature cannot 

 go? The chemist images that there is a limit, and he 

 calls the ultimate piece of matter which nature does 

 not divide an atom. No eye has ever seen an atom, 

 no microscope can ever render it visible. The mote 

 that dances in the sunbeam is composed of millions 

 of atoms. The spectroscope enables us to detect the 

 Viso, 000,000 of a grain of sodium, and this small speck 

 of sodium must contain millions of atoms in order to 

 color the flame sufficiently to render the sodium 

 visible. 



A grain of musk, it is said, will scent a room for 

 years without losing an appreciable amount of its 

 weight, and yet during this time the air in the room 

 has changed many times, and the molecules of musk 

 have been disseminated through the vast volume so 

 that the sense of smell could detect their presence. 

 What an enormous volume of air a little of the 

 musk from the skunk will vitiate, and yet this is only 

 possible by the almost infinite smallness of the 

 molecules. 



Nobert has drawn 4,000 lines on the breadth of one 

 millimetre, which is more than 200,000 lines to the 

 inch. A film of silver has been obtained 1 /i«i,ooa of 

 an inch in thickness, and films of platinum and gold 

 have been obtained Yi26,ooo of an inch in thickness, 

 and yet it is probable that this thickness contains 

 many atoms. 



The thickness of the soap-bubble at the dark part 

 just before it breaks, is 1 /m of the length of the 



