384 THE WORLD OF LIFE 



becomes greater, and the vast numbers and marvellous diversity 

 of the organic compounds becomes to some extent intelligible. 

 Professor Kerner, referring to the three substances just men- 

 tioned, 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 to- 

 gether 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 



H— C I 1 C— H H— C I I C— H 



H— C I I C— H H— C I I C— H 



c c 



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." 



