23(5 PHILOSOPHICAL TRANSACTIONS. [aNNO 1765. 



experiments wliich he had collected, for a larger work on that subject; and for 

 wViich, as opportunity offered, he had afterwards collected materials. And being 

 desirous that some of his observations should be further verified, and more fully 

 ascertaine<l before they were made public, he had then declined the honour of 

 having those Essays published in the Phil. Trans., esteeming it sufficient, at that 

 time, to have excited several of his friends, and among these. Sir Hans Sloane, 

 and the Rev. Doctor Hales, to communicate to him their sentiments on this 

 subject. 



In one of those essays he had occasion to remark, that a more intimate ac- 

 quaintance with damps and other mineral exhalations might lead to a discovery 

 of the nature and origin of those subtile and volatile principles, which enter the 

 composition of various mineral waters, and are stiled their spirit; on which 

 their chief virtues are found to depend; and that some of those waters seem to 

 be impregnated with exhalations that nearly resemble the fulminating-damp; 

 which, by its explosions, is found so destructive in coal-mines: while other 

 waters are more evidently saturated with that most subtile and active exhalation, 

 ■ which, in many places perspires from springs and lakes, and other openings of 

 the earth ; or arises in pits and mines, where it is discovered by extinguishing 

 flame; and, from its pernicious effects, in killing all animals that breathe 

 therein, is known to our miners by the name of choak-damp. This mephitic 

 exhalation he long ago discovered to be a particular kind of air, or permanently 

 elastic fluid ; and, from various observations and experiments related in the above- 

 mentioned Essays, had reason to conclude, that it enters into the composition of 

 the waters of Pyrmont and Spa, and of all others which, from their sharp and 

 pungent taste, are stiled acidulae; and that it constitutes the volatile principle of 

 those waters, called their spirit, on which their prime virtues chiefly depend j 

 although it has hitherto evaded the inquiries of the most skilful chemists, who 

 have not been able to retain it in their vessels; neither have they discovered any 

 method of imitating it by their art. 



In order the more fully to ascertain a fact of such importance, and to obtain 

 a clearer knowledge of the nature of this spirit, he took the opportunity while at 

 Spa, to make a few experiments on those celebrated waters, as follow : 



Exper. 1. Having filled a common quart bottle with Spa water at the fountain 

 Pouhon, Dr. B. took a dried calFs bladder, made limber with oil, from which 

 he carefully pressed out the air, by twisting it round, then drawing its orifice over 

 the neck of the bottle, there tied it close, so as to leave an open communication 

 between the water in the bottle and the empty cavity of the bladder, while the 

 external air was excluded from both. He filled 2 other quart bottles with the 

 Pouhon water, and fitted them to bladders in like manner. These bottles stood 

 14 days during the month of July, in a warm room; where he often examined 



