350 Anatijils of the Hot Springs at Bath. 



rived from the gas difiused in small quantity through the 

 water. If this be the case, the application of the concen- 

 trated solution of iron should produce a much more distinct 

 effect upon ihe infusion ; but it has been shown (D) that 

 the gas destroys the colour of infusion of galls instead of 

 increasing it, which \Voiild be the effect if it contained oxide 

 of iron. 



(f/) About one gallon of the water was put into a vessel 

 of considerable depth, of which it occupied about two- 

 thirds : it was slightly covered, and remained about twenty- 

 four hours. It then retained its power of affording a peach- 

 blossom coloured precipitate with infusion of galls (X) in a 

 very considerable degree. 



It is remarkable that in this experiment the result should 

 have proved so different from that obtained in one where 

 the circumstances were similar, excepting only the form of 

 the vessel and the quantity of the water. When the water 

 was exposed with a broad surface, infusion of galls showed 

 no action on it (a) ; but here, even after eight hours longer 

 exposure, it detected oxide of iron. 



From this circumstance I began to suspect that some 

 change was produced by the absorption of oxygen, and 

 that It had not produced the same effect in this as in the 

 former experiment, on account of the quantity of the water 

 and depth of the vessel. There appeared, however, a strong 

 fact against this supposition ; viz. that iron is more easily 

 detected when highly oxygenated, whereas the reverse ef- 

 fect in this case was produced. 



To try the effect of atmospheric air, the following experi- 

 ments were performed : 



(e) A small quantity of the water was enclosed, while hot, 

 in a well stopped phial, with about one-fortieth of its volume 

 of atmospheric air. After four days the water remained per- 

 fectly transparent, but the addition of infusion of galls did 

 not afford the slightest appearance of its containing iron. 



{f) Another portion of the water was kept for the same 

 length of time in a well stopped phial, but without any air 

 except such as the water held in solution. Infusion of galls 



occasioned 



