12 POPULAR SCIENCE. 



they cannot explain. It was said of Cuvier, that when he got 

 hold of a living creature he did not know how to classify by 

 any certain assemblage of analogical signs, he put it in ra- 

 diata. Similarly we may affirm of chemists, that catalysis and 

 allotropism are two cupboards wherein they have been wont 

 to stow away certain facts undigested or unexplained. I have 

 said something about catalysis, so let that pass; allotropism 

 needs more attention. Literally, allotropism or allotropicity, 

 when translated into plain English, is a very startling thing 

 indeed ; meaning little else than expression of the fact, or 

 rather belief, that some one thing may be some other thing, 

 and yet remain the same thing. I will give an illustration. 

 Everybody knows that the diamond to look at is very differ- 

 ent from a lump of charcoal to look at, and both different 

 from a piece of black-lead. This is physically evident ; yet 

 chemistry, apply it as we may, .only proves that the diamond, 

 charcoal, and black-lead are one and all carbon. If a diamond 

 be actually burned in oxygen gas, carbonic acid results ; the 

 very same gas we obtain by the combustion of charcoal in a 

 stove. More evidence: by exposing diamonds to heat in a 

 certain way, they can be changed to coke ; but unfortunately 

 for the practical man, and happily for ladies who have in- 

 vested in diamonds, proud of the investment, no means have 

 yet been discovered for effecting the backward change of 

 coke into diamonds. Enough for our purpose. Here, then, 

 we have an agent, an element that element carbon, assum- 

 ing three forms. Chemically, the element carbon is the same ; 

 physically it is not the same. How shall the puzzled chemist 

 describe the sameness and un sameness I He has invented the 

 words allotropism, allotropic, allotropicity, to this end. A man 

 who has done his best should not be blamed because the best 

 is imperfect. 



Carbon is not the only element that can assume allotropic 

 changes. Oxygen is in the same category, allotropic oxygen 

 having the specific name ozone a name that I am surprised 



