VOL. L.] PHILOSOPHICAL TRANSACTIONS. 95 



heat. But if the salt had been dissolved, filtrated, and crystallized, till it had 

 been purified and freed from this terrene matter, it would then certainly have 

 had the same appearance on the red-hot iron, as a pure aluminous salt. Again? 

 as it is peculiar to an aluminous salt to liquify in some degree with fire, so we 

 see that this was evidently the case of this salt. Its eliquation indeed could not 

 be so remarkable as in pure alum, because of its being mixed with so much earth; 

 but that it did liquify in some degree is plain, because the whole mass of salt and 

 earth, even when reduced to a powder, ran all together like a cinder. The ex- 

 periment on the solution of this salt with ol. tart. p. d. is also a further proof 

 of what we have already asserted : for though there was no visible effervescence, 

 yet the bubbles of air show that there was an intestine conflict of the oil with 

 the acid principle in the solution : which being absorbed by the alkali, the earth 

 was precipitated, to which it formerly adhered. 



The next 2 experiments were made to discover whether an acid or alkaline 

 principle prevailed in the water. 



Exper. 34. Forty drops of the syrup of violets being added to 1 oz. of the 

 water^ the mixture became of a bright sea-green colour. 35. A quantity of the 

 water being kept boiling for 5 minutes, and afterwards allowed to stand till it 

 became clear, was carefully filtrated from its ochrous sediment : after which, on 

 its mixture with syrup of violets, it turned of a faint reddish colour. 



From these experiments he inferred that this mineral water contained both an 

 alkaline and an acid principle ; the former consisting of the ochrous and ferrugi- 

 neous parts, which were separated from the water by elixation ; and the latter of 

 the aluminous salt, which remained in the water after elixation. 



The following trials were made, to know what effects are produced in the 

 water by being exposed to the air ; and in what respects the waters of the two 

 springs differed from each other. 



Exper. 36. An English quart of the water of each of the springs being fully 

 exposed to the air in 2 China bowls, the next day that of the under spring was 

 neither altered in its taste, colour, or transparency, nor in any other shape what- 

 ever ; but that of the upper spring appeared of a yellowish colour, though it was 

 clear and transparent as the other. 



On the 2d day the taste of the waters scarcely appeared to be any way dimi- 

 nished. No sensible change could be observed in the lower water ; but the upper 

 water was become more yellow than it was the day before,, yet without any loss 

 of its transparency. They both tinged of a deep blue colour with galls ; which 

 tinctures appeared equally deep and strong, as they did before the waters were 

 exposed to the air. The 3d day the lower water appeared clear and colourless as 

 before, only its surface was covered with a few small spots of cremor. The upper 



