VOL. L.] PHILOSOPHICAL TRANSACTIONS. 03 



heat, and after it was cool being filtered quite clear from its ochrous matter, it 

 still retained a subacid and aluminous taste in a very strong degree. 18. To an 

 oz. of common spring-water were added 2 drops of fresh sweet milk. This mix- 

 ture being shaken, the milk mixed intimately with the water, without any kind 

 of coagulation. IQ. The same experiment being made with the mineral water, 

 the milk, on its affusion, was so curdled, or separated into clouds, that the 

 greatest shaking could not mix or incorporate it with the water. 20. This ex- 

 periment being also made with a weak solution of alum in spring-water, its effects 

 on the milk were not in the least different from those of the mineral water. 21. 

 And the same trial being again repeated with the water, when boiled and filtred 

 from its ochrous parts, the milk was in the same manner coagulated as before 

 elixation. 22. One part of sweet milk being added to 4 parts of the mineral ' 

 •water, the milk subsided, and formed a cloud in the bottom of the glass, leaving 

 the upper parts of the water clear. This mixture being well shaken, the milk 

 mixed so well with the water, that it appeared to be but a very little curdled. 

 23. When a larger quantity of milk was added to a smaller quantity of water, 

 and even when equal parts of the milk and mineral water were mixed and shaken 

 together, no curdling or coagulation was observed. 24. An equal quantity of 

 the water and milk being boiled together, the greatest part of the milk was coa- 

 gulated into a thick white curd ; and the remainder, with the mineral water, 

 turned of a pure white milky colour, which drank like whey, and was very 

 agreeable. 25. Eight drops of sweet milk being added to 4 oz. of the water, and 

 the mixture boiled, part of the milk was curdled, and swam on the top of the 

 water. The ochrous parts of the water were likewise separated, and falling to 

 the bottom, their colour did not appear of a clear yellow, as usual, but was some- 

 thing milky. 



All these experiments strongly indicate the existence of alum in this water. 

 It retains its aluminous taste, and coagulates milk, after the chalybeate parts are 

 almost all expelled by elixation. The coagulation of the milk demonstrates an 

 acidity in the water, and the other appearances show that acidity to be awing to 

 an aluminous salt. 



The following experiments not only (the author thinks) ascertain the existence 

 of alum in the water with greater certainty, but also that there is a particular 

 kind of earth conjoined with this salt. 



Exper. 26. An English quart of the water being kept boiling for a quarter of 

 an hour, it turned thick, muddy, and yellow, by the separation of its ochrous 

 parts ; and, being set to cool in a clean bowl, the next day all the ochre was 

 subsided to the bottom, from which the water was carefully filtered : by which it 

 became almost as clear and limpid as before the elixation, retaining a sharp alu- 

 minous taste, but was deprived of the strong ferrugineous taste which it had at 



