159 



Miscellanea. 



[April 



" The excess in No. 2, is doubtless owing to the irregularity of the 

 rocky admixture in different specimens, whereof one yielded 44, and 

 another only 13.9 of insoluble matter, on digestion in acid. 



" The richness of the last of the three minerals will more than com- 

 pensate for the increase of trouble and expence in the reduction of the 

 ore by successive roastings 5 and practical miners assert, that the 

 glance or grey sulphuretis a much steadier and more plentiful ore than 

 the carbonate. 



" I should add, before concluding the above imperfect analysis of the 

 Nellore copper ores, that I tested them in vain for silver and other 

 metals. Neither did arsenic appear to be present. 



" I may here mention, that among the specimens of minerals present- 

 ed to me by Mr. Kerr, as occuring within the copper mining district? 

 associated with the micaceous schist, are the following; corundum and 

 adamantine spar, garnets, dark-green actinolite, red chalk, manganese ; 

 besides carbonote of maguiesia, and other minerals of which specimens 

 have not yet reached me. An ore of mercury is also suspected to exist 

 in the same range of rocks. The surface of the gneiss or micaceous 

 schist, where exposed to the air, is frequently seen tinged of a green 

 colour, from the trickling of water holding carbonate of copper in solu - 

 tion, through crevices of the rock." 



7. Water of the well zem-zem at Mecca. 



May 14. — A paper was read, entitled, " An Account of the Water 

 of the Well Zem-zem, with a qualitative analysis of the same by Pro- 

 fessor Faraday" ; in a letter from John Davidson, Esq., to the Se- 

 cretaries, and communicated by them. 



" The author having, during his stay at Jedda, the port of Mecca, suc- 

 ceeded in procuring about three quarts of the water from the well of 

 Zem zem, to which the Mahomedans ascribe a sacred character and 

 extraordinary virtues ; and wishing to preserve this water for the pur- 

 poses of analysis, had the can in which it was contained carefully seal- 

 ed; but, unfortunately, on its arrival in the London Docks, the can not- 

 withstanding the directions written on it, was opened, and the gas with 

 which it was highly charged, and by which it held in solution a very 

 large quantity of iron and other matters, was allowed to escape. The 

 precipitate thrown down, in consequence of the loss of this gas, w r as 

 found, by Professor Faraday, to consist of carbonate of protoxide of iron 

 in the enormous proportion of 100.8 grains to the imperial pint of water. 

 The clear fluid was neutral, and contained much muriate, and a little 

 sulphate, but no carbonate ; together with a little lime, potash, and 

 soda. There was also found an alkaline nitrate in considerable quanti- 

 ty ; this Mr. Faraday conjectures to have been saltpetre, which had 

 been added to the water by the priests." 



Transactions of the Royal Society. 



