THE PURPOSE OF DIVERSITY 389 



medicine or in the various arts, and their numbers are 

 very great. They are usually divided into two classes, the 

 inorganic and the organic ; the former being of the same 

 nature as those of the great bulk of the mineral species, 

 while the latter, called also carbon -compounds, resemble 

 the products of living organisms of which carbon is an 

 essential part. 



A recent estimate of the known inorganic compounds, 

 natural and artificial, by a French chemist is 8000 ; but 

 Mr. L. Fletcher, of the British Museum, informs me that 

 this number must only be taken as an " irreducible minimum." 

 As to organic compounds, I am told by Professor H. E. 

 Armstrong, that they have recently been estimated at about 

 100,000 ; but he states that the possibilities of forming such 

 compounds are infinite, that chemists can make them by the 

 thousand if required, and that they now limit themselves to 

 those which have some special interest. The approximate 

 figures for the various kinds of stable chemical compounds 

 now known, will therefore form an easily remembered 

 series : 



Mineral species ...... 1,000 



Inorganic compounds (artificial) . . . 10,000 



Organic compounds (artificial) . . . 100,000 



Possible organic compounds .... Infinite ! 



What a wonderful conception this affords us of the 

 possibilities of the elements (or rather of about one-fifth of 

 them) to produce the almost endless variety of natural 

 products in the vegetable and animal kingdoms. These 

 possibilities must depend upon the "properties" of the 

 elements ; not only their actual properties as elements, but 

 their latent properties through which they not only com- 

 bine with each other in a great variety of ways, but, 

 by each combination create, as it were, a new substance, 

 possessing properties and powers different from those 

 of any other substances whatever. These almost infinitely 

 various properties of chemical combinations, together with a 

 host of other problems with which the organic chemist has 

 to deal, have led some of them to almost exactly the same 

 conclusion to which I have been led by a more superficial 



