VOL. XXX.J PHILOSOPHICAL TRANSACTIONS. 281 



Take a very little gall [nut-gall] in powder, about half a grain to a glass of a 

 quarter of a pint ; this in a moment renders it turbid, and makes a dark purple, 

 especially when stirred : but if you drop the powder on the surface of the same 

 water, it then causes a fine blue tincture. To make a very fine tincture, take 5 

 leaves of strong green tea, put them into the bottom of a glass holding a 

 quarter of a pint, and you will see those leaves unfold themselves, and in a 

 quarter of an hour, tinge the water with such a cerulean or azure blue, that 

 few vegetables afford the like. The longer these leaves, or any other styptics, 

 (which are the precipitants) stay together, the more they degenerate into a deep 

 purple, or even to an atramentous colour. 



As to the internal use of these waters, I drank about a quart at a time, in 

 the following manner : I first began with Spa-waters, which 1 procured very 

 good, and drank them for a week, and they agreed very well. I then drank 

 the Pyrmont waters for 3 or 4 days, and continued the use of these waters 

 alternately for 20 days. By the result of my experiments it seemed to me very 

 plain, that the Pyrmont water was more agreeable, gave more strength and 

 spirit, and was as much or more preferable for its internal virtue, as for its 

 excelling the other in a brisker and more sprightly taste.* 



There is another excellency in these waters, which will make them more use- 

 ful to us, than any foreign chalybeate waters we yet know ; that is they will 

 keep better, and are not so soon spoiled by any accidental insinuations of air, 

 as the Spa are subject to be. The chalybeate mineral is here thoroughly dis- 

 solved, and well united and mixed in this water, so that it does not easily pre- 

 cipitate : for which reason it may also the better pass the vasa lactea, and even 

 enter into the mass of blood itself, and work the more considerable effects. 

 That this is not a bare hypothesis may be proved by the following experiment. 



Having suffered the Spa-water to be exposed in a bottle which was half full, 

 and unstopped 12 hours, I examined it, and found it tasted just like common 

 water; but the Pyrmont waters that were opened to the air in the same manner, 

 tasted strong of the mineral, and gave their tincture as at first ; nay, they con- 

 tinued thus for full 2 days, and perhaps might have done so longer. 



Hence I may fairly conclude, that since the Spa has been very beneficial to 

 our patients in chronical diseases, these waters, of a much superior virtue, will 

 surpass them in conquering many of our obstinate distempers. 



* The Spa water, like the Pyrmont, is a carbonated chalybeate water ; but the latter is more 

 strongly impregnated with carbonic acid gas. The proportion of iron, according to Bergman, is the 

 same in both j but the saline ingredients (in addition to the carbonate of iron) in the Pyrmont water, 

 are in greater variety and quantity, than those contained in the Spa water. See Bergman's Chemical 

 Essays translated by Cullen, vol. i, pp. 249-253. 



VOL. VI. O O 



