•(> Diimoiids. Kew Picccfs of Tunmtig . 



and its matrix li cither fat quartz or fine-grained tender cos, micaceous gneis, or the quart - 

 zofc ore ol" iioii, tzfhus fnniis Linn. 



The exploring of diamonds is performed by changing the beds of ftreams, in order 

 that the fand or gravel may be wailicd, and the di;imonds fclefted; or by breaking the 

 j-dyW^'O with large hammers, and iifccrwards wafliing it in troughs. This wafliing differ* 

 from that of gold, bccaufe it requires a finall quantity of very clear water, and very little. 

 of the cajialho at a time ; proportions which are pretifely contrary to thofe required in 

 waQiIng gold. Black flaves arc employed in this bufinefs, entirely naked excepting a clotlt 

 round their middle, in order that they may not embezzle any of the diamonds ;. but in fpitc 

 of every precaution, and the vigilance of numerous infpeclors, they ncverthelefs find 

 means of concealing them, which they fell at a very low price, to the interlopers, for 

 tobacco and rum. 



This is all the informntion I can with certainty Rate rcfpecliiig diamonds. I have only 

 to remark, that other provinces likcwife afford them ; as Cuiaba, ar,d the dillricls of Guara. 

 puara, in the province of St. Paul ; but thefe parts arc not exploi-e«l. 



VL 



Ahjtracl of the Spccijication cf Mr. IFillIAM DesMOSD's ruw I\LthoJ of Tatitiiiig ; luilJi 

 Obfervations relctivc to that Subjecl. 



E 



ARLY laft year * a patent was taken out by Mr. WilHam Defmond for the metliod 

 or procels of tanning praitifed, as it is faid, with great fuccefs in France by Seguin. The 

 fubilancc of Mr. Defmond's fpecification is as follows : 



The art of tanning confifts in impregnating fkiiis with a principle obtained from tan, witli 

 which they form a compound, infoluble in water, and pofi'eirmg other qualities well known 

 in the fubllance called leather. He obtains the tanning principle by digeftlng oak-bark, or 

 other proper material, in cold water, in an apparatus nearly fimilar to that ufed in the falt- 

 pctre works. That is to fay, the water which has remained upon the powdered bark for a 

 certain time, in one vefTel, is drawn off by a cock, and poured upon frelh tan. This is 

 again to be drawn o(F, and poured upon other frefh tan ; and in this way the proccfs is to 

 be continued to the fifth vedel. The liquor is then highly coloured, and marks, as Mr. 

 Uefmond fays, from fix to eight degrees on the hydrometer for falts -j-. He calls this the 

 tanning lixivium. The criterion to diftinguifh its prefence is, that it precipitates glue 

 from its aiiueous folution, and is alfo ufeful to examine how far otlier vegetable fubflances, 

 as well as oak-bark, may be faltable to the purpofe of tanning. The (Irong tanning liquor 

 is to be kept by itfelf. It is found by trials with the glue, that the tanning principle of 

 the firft digeftcr which receives the clear water, is, of courfe, firil exhaufted. But tlie 

 fame tan will ftiU give a certain portion of the aftringent principle, or gallic lixivium, ta 



Jan. 15, 1705. 

 t Probihly that of Bauirc, defcribcd in lii> Elcmens ilc Pharmacic. For tht corrcfponding fpccific gravit/ 

 '« !hc ufual focm, fee p. 39 of tliisjouinal. 



wateii 



