370 Mr. Voysey on the Diamond Mines 



them as well as 1 could between two pieces of polished glass ; 

 they always appeared globular, but less, and more greedy of 

 water than before. I do not doubt but that these globules 

 contain, like salts, a water of crystallization. 



" I had to examine the fine flour of wheat in order to com- 

 pare the molecules of it with those of the potatoe ; they are 

 smaller, and are rendered more irregular, by globules and by 

 shapeless molecules in the wheat. I cut some transversal 

 slices very thin of a grain of wheat ; round and very uniform 

 globules then appeared, but three times smaller than the 

 globules of the potatoe ; for they wei'e only from ^j-Q to T ^ of 

 a line in diameter. Neither hair-powder, nor starch in empois, 

 seen through the microscope, essentially differs from flour. 



" I do not presume that this diminutiveness is the only cause 

 which renders flour fit for powder ; but heat does not change 

 it so easily as the fecula of potatoe : it contains less water ; it 

 is also less quick in losing and regaining it. Also potatoe- 

 bread keeps fresh but two or three days, that of wheat from 

 four to eight days ; whilst rye bread keeps fresh at least from 

 fifteen to twenty days, even a month, when the bran is left 

 with it, at least, in part." 



LVII. On the Diamond Mines of Southern India. By 

 H. W. Voysey, Esq.* 



TTAVING lately visited some of the principal diamond 

 -*- J mines of Southern India, the few facts I have been able 

 to collect respecting the geological relations of that gem, I 

 take the liberty of laying before the Asiatic Society. 



A knowledge of the matrix of the diamond has long been 

 a desideratum in mineralogy. It has been hitherto supposed 

 that this mineral was only found in alluvial soil ; and a late 

 writer infers from some circumstances attending a particular 

 diamond, which had passed under his examination, that the 

 matrix of this precious stone was neither a rock of igneous 

 origin nor one of aqueous deposition -j* , " but that it probably 

 originates like amber, from the consolidation of perhaps ve- 

 getable matter, which gradually acquires a crystalline form, 

 by the influence of time, and the slow action of corpuscular 

 forces." 



This reasoning may apply with justice to the particular 

 specimens which have fallen under the observations of Dr. 

 Brewster, but as it is fully ascertained that diamonds have 



* From the Bengal Asiatic Researches, vol. xv. p. 120. 

 f See Quarterly Journal of Science and Art, Oct. 1820. 



for 



