MEJIOIK XX.] THE ALLOTROPISM OF CIILOHINK. 035 



Association some of the facts. The connection of these 

 zperiments with the discussion between the theory of 

 substitutions and the electro-chemical theory is obvious. 



Very recently M. Berzelius has published an impor- 

 tant paper on the allotropism of simple bodies, the ob- 

 ject of which is to point out that many of those bodies 

 can assume different qualities by being subjected to cer- 

 tain modes of treatment. Thus carbon furnishes three 

 forms charcoal, plumbago, and diamond. 



To a certain extent these views coincide with those 

 which have offered themselves to me from the study of 

 the properties of chlorine. They are not, however, al- 

 together the same. M. Berzelius infers that elementary 

 bodies can, as has been said, assume under varying cir- 

 cumstances different qualities. The idea which it is at- 

 tempted to communicate in this Memoir is simply this, 

 that a given substance, such as chlorine, can pass from a 

 state of high activity, in which it possesses all its well- 

 known properties, to a state of complete inactivity, in 

 which even its most energetic affinities disappear. And 

 that between these extremes there are innumerable in- 

 termediate points. Between the two views there is, 

 therefore, this essential difference: from the former it 

 does not appear what the nature of the newly assumed 

 properties may be ; from the latter they must obviously 

 be of the same character, and differ only in intensity or 

 degree diminishing from stage to stage until complete 

 inactivity results. 



In the case of chlorine the same activity which is com- 

 municated by the indigo rays can also be communicated 

 by a high temperature, or by the action of platinum. 



The points which this Memoir is intended to establish 

 are 



I. That chlorine gas can exist under two forms. In 

 the same way that metallic iron can exist as active or 



