238 PHILOSOPHICAL TKANSACTIONS. [aNNO 1765. 



foregoing experiments: he also relates, that the air seemed to arise from the water 

 with some degree of force, and continued long in an elastic state. The same 

 experiment was since tried, by Dr. Home, on the chalybeate waters of Dunse in 

 Scotland i* who collected considerable quantities of true permanent air from 

 those waters ; which he conjectures in no respect to differ from the common air 

 of the atmosphere. And as Dr. B. had no doubt of the accuracy and fidelity of 

 those gentlemen in their experiments; and had entertained an opinion that the 

 most spirituous acidulae contained the most air, which, it was reasonable to sup- 

 pose, might be separated from them in the same manner that it was separable 

 from those that were less spirituous; he therefore was greatly disappointed in his 

 expectations, when he could not obtain any air from the Pouhon water after the 

 manner above related. He did not, however, conclude, till after repeated trials, 

 that air does not spontaneously separate from the Pouhon water, in such manner, 

 and in so short a time, as it is said to separate from the Dunse and Scarborough 

 waters; and that, when excluded from the common air, it will, for several days, 

 bear the greatest heats of the summer, usually found in the shade, at Spa, with- 

 out parting with any of the air, or other principles of which it is composed. It 

 is, however, manifest, that, by the heat applied in the above experiments, the 

 Pouhon water was disposed more readily to part with its air, or some other elastic 

 substance, than it is when taken cool from the spring; seeing that, when poured 

 into a glass, after it had been thus heated, it sparkled more than when fresh 

 drawn from the fountain, and flew with more violence when shaken in a bottle. 



We may also hence learn, that when bottles filled with the acidulae are broken 

 in hot, sultry weather, accompanied with thunder, as Hoffman and others have 

 observed them, this accident must rather proceed from other causes, than from 

 the expansion of their subtile mineral spirit, to which it is usually attributed. 

 That flasks filled with the Pouhon waters, are liable to such accidents when un- 

 skilfully closed up, those who fill them for exportation, have learned from expe- 

 rience. To prevent which, they suffer the flasks, after they are filled, to remain 

 several hours in a warm air before they cork them up. And he found, that one 

 of those flasks being filled to the neck, at the Pouhon spring, when Fahrenheit's 

 thermometer stood therein at 53 degrees, the water had arisen near \ of an inch 

 in the slender neck of the flask, after it had stood, thus filled, for 3 hours, in a 

 heat of 76 degrees; which rarefaction of the water, by the common heat of the 

 air in summer, was more than sufficient to have broken the flask, had it been 

 filled quite full with the water, and immediately closed at the fountain. 



Exper. 1. Dr. B. took one of the long Frontiniac phials, which might contain 

 about 21 oz. avoirdupois weight of Spa water, and which had stood ^ days in ex- 



• Essay on the Contents and Virtues of Dunse Spa, Edinburgh, 1751, p. 9^, &c, — Orig. 



