Faraday to Jacob Herbert   14 April 1847

Royal Institution | 14 April 1847

My dear Sir

The last portion of Bardsey water which you sent me¹ in a gallon stone bottle (broken & only half full) correspond with the former² in general character. It was quite in a state of fermentation from the quantity of organic matter that had been & was in it & smelt alcoholic like a weak cyder. The unchanged organic matter still in it gave it a clear brown colour. There was also sulphate of magnesia present. But the most striking thing respecting it was the deposition in the bottle. Suspecting that something of the kind had occurred I broke open the bottle & found deposited at the side & bottom a thick crust of Carbonate of magnesia which when collected & dried weighed 230 grains[.]

I think it is almost impossible that the whole of this could have been deposited from the gallon of water which the bottle would hold & suspect the vessel has been in use as a recipient for the water & has been filled & emptied many times in succession & thus allowed an accumulation of deposit[.]

The water however is manifestly subject to the presence of organic matter & also of Magnesium salts & though experience only can tell whether these are unhealthy or not still one cannot say in any case that such a water is good or fit for use. If the whole of the deposit was from one gallon of water, the water cannot be wholesome.

I am My dear Sir | Very Truly Yours | M. Faraday

Jacob Herbert Esq | &c &c &c