346 Prof. Bischof on the Temperature of 



silica and sulphuretted hydrogen, would be produced ; for those 

 springs contain very little of these substances. 



The formation of mineral springs by the decomposition of 

 water by the alkaline metals, is, indeed, contradicted by the cir-' 

 cumstance that, in that case, streams of hydrogen gas must issue 

 with the water, which has not as yet been observed in any 

 springs. 



There is also another argument against the possibility of any 

 chemical process being the cause of the heat of thermal springs, 

 which is in some cases so very considerable, namely, that it is by 

 no means a general rule that those springs, which contain the 

 greatest quantity of fixed substances, are the hottest. Thus^ for 

 example, within the space of about one mile, in the vicinity of 

 the Laacher See, are found the following mineral springs, whose 

 quantities of fixed constituents and temperatures confirm my 

 assertion, at least for that neighbourhood. 



Heilbronn, 

 Tonnistein, 

 Fehlenbor, 

 Burgbrohl, I. 

 Burgbrobl, II. 



Still less is it the case with the alpine springs Gastein and 

 PfafFers, which contain less fixed and gaseous substances than 

 common spring water, and are consequently little else than pure 

 warm water ; not to mention the pure water springs and arte- 

 sian wells, which are frequently warmer than neighbouring mi- 

 neral springs containing fixed substances in great abundance. 



If there existed mineral springs consisting of a concentrated 

 solution of sulphate of iron, a superior temperature would be 

 more conceivable ; although even then the elevation could hardly 

 be perceptible, as the slow decomposition of the magnetic pyrites 

 in the copperas manufactories proves. 



Against the second case, namely, that chemical processes take 

 place in the vicinity of the course of mineral waters, by which 

 the sides of the hollows and clefts through which they flow be- 

 come heated from without, several objections may be made. In 

 the first place, traces of such chemical processes would surely 

 be visible, if the seat of their action were in communication, by 

 means of the clefts, >vith the surface. But in that case, the 



