94 ORIGIN AND NATURE OF LIFE 



be made up of two atoms of carbon and 

 four of hydrogen. So such an apparent 

 exception is accounted for, as can all similar 

 cases. 



Coming now to direct evidence as to the 

 tetra-valeat nature of the carbon atom, it 

 is found that the clearest proof is given by a 

 series of compounds between carbon, hydrogen 

 and chlorine, in which there exists only one 

 atom of carbon in the molecule of each com- 

 pound, and the hydrogen can be replaced in 

 four stages by the chlorine in such a way 

 that it is demonstrated that there are four 

 atoms of hydrogen in the compound which 

 has most hydrogen and four atoms of chlorine 

 in that which has most chlorine. 



The compounds can be represented by the 

 following scheme, but it must most carefully 

 be remembered that the atoms are not really 

 linked or hooked together, but probably many 

 hundreds of times their own dimensions 

 removed from one another. It is the energy 

 properties of the carbon atom which in some 

 unknown way enable it to remain in balanced 

 equipoise with four of these univalent atoms, 

 and never with more or less than four 

 of them. In the formulae, or symbols, C 

 stands for carbon, H for hydrogen, and CI for 

 chlorine : — 



