MEMOIK XXVII.] THE EFFECTS OF ALLOTROPISM. 375 



MEMOIR XXVII. 



ON THE EXISTENCE AND EFFECTS OF ALLOTROPISM ON 

 THE CONSTITUENTS OF LIVING BEINGS. 



From the Philosophical Magazine, April, 1849. 



CONTENTS : Allotropism of elementary substances. FranJcenheim* s no- 

 menclature. Brought about by light , heat, electricity, and by the ner- 

 vous principle. Explanation of inflammation and congestion. 



IT has been completely established for the majority 

 of elementary substances that there are several forms 

 under which each may occur forms differing entirely 

 both in their physical and chemical relations. 



Thus, in the case of carbon, many such forms are 

 known. To three of them Berzelius has directed at- 

 tention : 1st, ordinary charcoal; 2d, plumbago; 3d, dia- 

 mond. They are three distinct modifications of the same 

 element. They differ in specific gravity, in specific heat, 

 and in conducting power, both for electricity and caloric. 

 In their relations to light, the first perfectly absorbs it, 

 and is black; the second reflects it like a metal; the 

 third is transparent like glass. When crystallized, plum- 

 bago and diamond do not belong to the same system : 

 their chemical relations are also strikingly different. 

 Charcoal takes fire with facility, and some varieties of it 

 are even spontaneously combustible in the air ; but cru- 

 cibles and furnaces are made of plumbago because of its 

 incombustibility ; and the diamond with difficulty is set 

 on fire in pure oxygen gas. 



It seems immaterial to what class elementary bodies 

 belong, whether electro - negative or positive: they pre- 



