62 



DIVISIBILITY OF MATTER. ATOMIC THEORY. 



PHYSICAL SCIENCE, in all its parts, is ever furnishing 

 fresh instances to amaze and bewilder our conceptions 

 on this subject. They tax heavily the belief of com- 

 mon minds, though sustained by evidence irresistible in 

 kind, as compulsory as mathematical demonstration. 

 Examples of the divisibility of matter are now so 

 numerous and familiar that it is needless to dwell upon 

 them ; yet a few may be cited instar multorum, and 

 these derived chiefly from recent researches. 



Take sodium as indicated by its coloured lines in 

 the spectrum. Calculation, based upon the diffusion 

 of a salt of this metal in a given atmospheric space, 

 shows that 180-millionth part of a grain of sodium 

 may be detected by this subtle analysis. In the sodium 

 salt thus employed other experiments prove the pre- 

 sence of one ten-millionth part of iodine as an ingre- 

 dient. Take aniline as an example from modern 

 chemistry. A single grain gives a rose-pink colour to 

 ten million times its weight of water, by diffusion of 

 the innumerable molecules of aniline of which this 

 grain is composed. In like manner a strong ruby tint 

 is given to a volume of fluid by a quantity of gold not 

 exceeding -gj^^f part by weight. 



