THE PURPOSE OF DIVEESITY 419 



the surface by volcanoes and liot springs, renders it prol>:d)lo 

 that very few either of the elements or compounds remain 

 unknown. 



The skill of the chemist, however, has led to the production 

 of a much greater number of stable chemical compounds than 

 occur in nature. These are used in medicine or in the various 

 arts, and their numbers are very great. They are usually 

 divided into two classes, the inorganic and the (jrganic; the 

 former being of the same nature as tliose of the great bulk of 

 the mineral species, while the latter, called also carbon-com- 

 pounds, resemble the products of living organisms of which 

 carbon is an essential part. 



A recent estimate of the known inorganic compounds, 

 natural and artificial, bv a French chemist is 8000 ; but ^Ir. 

 L. Fletcher, of the British [Museum, informs me that this 

 number must onlv be taken as an '' irreducible minimum.'' 

 As to organic compounds, I am told by Professor II. E. Arm- 

 strong, that they have recently been estimated at about 100, 

 000 ; but he states that the j^ossihilities of forming such com- 

 pounds are infinite, that chemists can make them by 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 possi- 

 bilities of the elements (or rather of about one-fifth of them) 

 to produce the almost endless variety of natural products in 

 the vegetable and animn! kinirdoms. Tliese possibilities must 

 depend upon the "properties" of the elements; not only their 

 actual properties as elements, but their latent pntperties 

 through which they not only combine with each other in a 

 great variety of ways, but, by each eombi nation create, as it 



