Dr Petzholdt on (he Formation of the Diamond. 319 



naturally ascribe the cracks, &c.,to the blows received during 

 the transport of so hard and brittle a substance as diamond, 

 and the external scaling off is solely owing to imperfect crys- 

 tallization, for the instances of it I have seen have always been 

 in the modified crystalline forms of the diamond (to which all 

 the Russian specimens examined by Parrot belong), and never 

 in the simple octahedrons. 



GiJbeFs* view of the oi'igin of the diamond is, it is true, 

 supported by chemistry, in so far that carbon can be obtained 

 from carbonic acid at a high temperature, by means of the 

 action of reducing substances, such as magnesium, calcium, 

 aluminium, silicium, or iron, and a direct experiment of mine 

 regarding the power of iron to reduce carbonic acid is also 

 in its favour;t but the geognostical relations in which diamonds 

 are found, by no means confirm this opinion ; for we either 

 find no phenomena whatever connected with the occurrence 

 of the diamond, which indicate so high a temperature as would 

 be requisite for the decomposition of carbonic acid, or where 

 such present themselves, as in the case of the dolomite of the 

 Ural, diamonds have not actually been found in the rock. \V^e 

 have not taken the fact into consideration, that when carbon 

 is separated from its combinations, as from carbonic acid, it is 

 always obtained in the form of a black powder. J 



Lastly, the opinion expressed by Hausmann§ must not be 

 passed over in silence, as it is the view entertained by so com- 

 petent a judge. According to him, electricity has operated 

 in the formation of diamonds, and that by lightning decom- 

 posing carbonic acid ; and the argument for this is, that, ac- 

 cording to the assertion of the oldest diamond seekers, fulgu- 

 rites or lightning tubes are most frequently met with where 

 the diamonds are most numerous. Though we should assent 

 to the possibility of such a decomposition under certain cir- 

 cumstances, yet we cannot regard as at all admissible, the 



* Englehardfs LafiersUitte dcr Diamanten, &c. ; the chemical portion of 

 that essay -was edited by Gobel, and an extract from it is published in Pog- 

 gendorfl''s Aimahn, 1830, vol. xx., p. 539. 



t See Petzboldt's Erdkunde {Geologit), p. 133. 



\ See Erdmann's Chanie, 1840, p. 133. 



S Ersch and Gruber, Allgemcine Enajclopcidic, article " Diamant." 



