14 



Such words show you far better than any of mine could, the 

 difficulty of this form of scientific belief. If Mind be evolved 

 from Matter there can be but one substratum, not two ; all the old 

 ideas must be incorrect, and this one substance possesses at the 

 same time two sets of opposite properties. I think we must allow 

 that this is but making a mystery more mysterious still. We shall 

 require a new definition of Matter, the nature of which however has 

 not yet been determined. 



MOLECULES AND THEIR MOTIONS. 



A mass of matter of any kind is supposed to be made up of a 

 number of minute bodies which are called molecules. We define a 

 molecule as the smallest possible particle of a substance that can 

 exist alone. It is in itself compound, often exceedingly complex, 

 being composed of still minuter particles called atoms ; but being 

 the smallest particle of a substance that we can even think about ; 

 the moment a molecule is broken up by chemical action its nature 

 is changed ; it enters into new arrangements and is no longer the 

 same substance. No person has ever yet seen a molecule, in aU 

 probability no one ever will ; the minutest grain visible under the 

 most powerful microscope contains thousands of them. Yet in 

 spite of this great disadvantage our scientific guides tell us they 

 have been approximately measured ; and the diameter of one 

 cannot be less than the 500 millionth part of an inch. The number 

 of them in a cubic inch of air at a freezing temperature would be 

 represented by the figure 3 with twenty ciphers after it, while a 

 drop of water, in which they would necessarily be packed more 

 closely together, contains a number represented by 100 followed 

 by twenty-four ciphers. The physicist, like the astronomer, deals 

 with numbers infinitely large, but he also deals with sizes infinitely 

 small. Now these particles are never at rest, they are always in 

 rapid motion even in the densest solid, but necessarily moving 

 within narrow limits ; so that even if we accept inertia as a pro- 

 perty of matter in the mass, it does not appear to be a property of 

 its constituent molecules, and therefore it is not an essential pro- 

 perty of matter, though our text books have always taught us that 

 it is. And again if we grant that the molecular movements are the 

 consequence of some primal force originally acting on them, but not 

 now, do we not get perpetual motion, which we are told is an im- 

 possibility ? In liquids the limits of vibration are wider than in 

 solids, but the greatest molecular freedom is found in bodies in 

 the gaseous condition, and here the rapidity is enormous. Accord- 

 ing to accepted calculations and experiments the particles of 

 hydrogen gas at a freezing temperature are moving about at the 



