356 THE WORLD OF LIFE 



arrangement of the atoms, and to their being combined and 

 recombined in different ways ; and as the more atoms are 

 used the possible complexity of these arrangements becomes 

 greater, the vast numbers and marvellous diversity of the 

 organic compounds becomes to some extent intelligible. 

 Professor Kerner, referring to the three substances just 

 mentioned, gives the following suggestive illustration of 

 their diverse properties, of which I have only mentioned 

 a few. He says : 



" If six black, ten blue, and five red balls are placed close 

 together in a frame, they can be grouped in the most diverse ways 

 into beautiful symmetrical figures. They are always the same balls, 

 they always take up the same space, and yet the effect of the figures 

 produced by the different arrangements is wholly distinct. It may 

 be imagined, similarly, that the appearance of the whole mass of a 

 carbon -compound becomes different in consequence of the 

 arrangement of the atoms, and that not only the appearance but 

 even the physical properties undergo striking alterations." 



Another and perhaps more interesting example, 

 illustrated by a diagram, is given by Mr. W. Bate Hardy 

 in his lecture already referred to. He says : 



" Here is a simple and startling case. The molecules of two 

 chemical substances, benzonitrile and phenylisocyanide, are com- 

 posed of seven atoms of carbon, five of hydrogen, and one of 

 nitrogen : 



N C 



I I 



C N 



I I 



c c 



H— C (\ C— H H— C /\ C— H 



H— C I I C— H H— C I I C— H 



c c 



H. 4 



Benzonitrile. Phenylisocyanide. 



The only difference in the arrangement of the atoms is that those 

 of nitrogen and carbon are reversed. But the properties of these 

 two substances are as unlike as possible. The first is a harmless 

 fluid with an aromatic smell of bitter almonds. The second is very 

 poisonous, and its odour most offensive." 



Here only three elements are combined, and in identical 



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