Report on the Progress of Chemistry. 147 



be taken out of the CH 4 , thus leaving the compound 

 CH 3 , and the chemical energy of the carbon is no longer 

 satisfied; there is a deficiency just equal to an atom of hy- 

 drogen. This deficiency may be supplied by restoring the 

 atom of hydrogen or by offering, instead, an atom of any 

 other substance which is equivalent to it. But for every 

 different atom received, a different compound is formed, 

 and thus the radical CH 3 , becomes a root, out of 

 which may spring a long series of compounds. Hy- 

 droxyl (HO) is another of these radicals. In it the com- 

 bining power of oxygen is not satisfied. Give it another 

 atom of hydrogen, and it becomes water (H 2 0), or in 

 place of this atom of hydrogen substitute a molecule of the 

 radical ethyl (C 2 H 5 ) and the water is changed to alcohol 

 (C 2 H 5 HO), hydroxyl being the common root of both. 



From a few such roots or radicals, nearly all organic sub- 

 stances, however complex, may be supposed to spring. 



The adoption of this elegant theory of quantivalence into 

 the science of chemistry has given a new impetus to the study 

 of organic bodies. It is found possible to classify them ac- 

 cording to the radical which may be thought to predominate 

 in their composition, and the vast multitude of these com- 

 plex substances is being gradually sorted and grouped ac- 

 cordingly. Series are thus formed, each based upon a 

 radical and built up from it by numerical ratios. This 

 work has a two-fold value: it enables the chemist to study 

 more successfully the characters of substances already 

 known to exist, and, at the same time, it suggests the direc- 

 tions in which new ones are to be discovered. For as in 

 Bode's law of planetary distances, one ratio had at first no 

 known planet to correspond to it, so in these chemical series, 

 there are numerical values with no known corresponding 

 compounds; and as the vacancy in Bode's series led to the 

 discovery of the asteroids, so these vacancies in chemical 

 series are constantly leading to the discovery of new com- 



