Dr Potzholdt on the Formation of the Diamond. 317 



Harbours of Refuge. This is, indeed, a subject which the 

 shipping interest, and the friends of humanity, are equally 

 bound to bring under the notice and favourable consideration 

 of the British public, and it will be to me a source of pure en- 

 joyment if the preceding remarks tend in any degree to the 

 accomplishment of an end in so many respects desirable. 



John Fleming. 



King's College, AberdeeNj 

 March 2. 1843. 



On the Formation of the Diamond. By Dr Alexander 

 Petzholdt, of Dresden. 



Notwithstanding the great diversity of opinion expressed 

 by authors regarding the mode of formation of the diamond, 

 yet all the different views entertained may be included under 

 two principal divisions, viz., those which suppose that it is the 

 direct product of the action of heat on carbonic acid or car- 

 bon, and others which support the idea of its being the result 

 of the slow decomposition of plants. It may not be out of place 

 to give a brief account of the most important of these views, 

 previous to communicating my OAvn observations. 



While Leonhard* asks, if we may not believe that the origin 

 of diamonds is to be ascribed to carbonaceous sublimations 

 from the interior of the earth, a question which must, on che- 

 mical grounds, be answered decidedly in the negative, because 

 carbon is not in the slightest degree volatile ; Parrott regards 

 diamonds as products of volcanic action, as the result of the 

 operation of the heat on small fragments of carbon. Parrot 

 was first of all led to this view, by his minute examiuiition 



* Leonhard's Populdrische Vorlesxtngen, vol. iii. p. 49a. 



t Parrot's Notice sur Ics dinmans dc I'Oural, in the Mbnoires de I'Acnlemie 

 Impmale des Sciences de St PHrrshonsr/. Sfrie dixidme. Sciences Jfal/ie- 

 matt'jues, torn, i., p. 32. He says, " Diamonds arc the products of vol- 

 canic action exercised on small jwrtions of carbon, or on a substance com 

 posed ol'mucli carbon and very little hydrogen. " Sec also Leonhard's Jahr- 

 bucli, IU38, p. 541, where portions of r.irrol's Memoir are published. 



