93 



It has been supposed that the iron pyrites scattered through 

 the New Red, or rather between the New Red and the Lias, 

 might by oxidation be the cause. But in the first phace this 

 oxidation giving rise to heat only occurs when the sulphuret of 

 iron is more or less pulverised and heaped together in masses. 

 When it occurs as it does near Bath, it has been dej30sited by 

 water, and is the result of the decomposition of carbonate of iron 

 by a sulphate, probably of lime, by which a sulphiu'et of iron is 

 deposited, and carbonate of lime formed and carried away. A 

 similar result has been proved to have occurred at the thermal 

 springs of Aix la Chapelle, where, in cleaning the spring basin, 

 fragments of Transition Limestone (between which and Grauwacke 

 the spring issues), were found covered with a thin coating of iron 

 pyrites. 



Bischof mentions another case where, at the enclosure of a 

 mineral spring, on taking away an old wooden tube that had 

 been previously used at the issue of the spring, and removing the 

 earth around it, dark yellow iron pyrites were found in it. 



We find also that the coal is in various places coated with 

 iron pyrites, therefore we conclude that the pyrites, when found 

 detached and scattered, are a result of the long continued action 

 of carbonated water dissolving the oxide of iron through the soil 

 or rocks, and then decomposed and deposited as a sulphuret by 

 the action of a sulphate, probably of lime, and that they cannot 

 therefore be looked on as a source of heat. 



The mineral constitution of the waters has thrown some light 

 on their source of supply, but not on their source of heat. Let 

 us see if the gaseous contents will lead us further. 



The King's spring yields about two and a half hogsheads of 

 water per minute, and evolves about 267 cubic inches of gas in 

 that time, of which nitrogen forms 97 per cent, to 3 per cent, of 

 oxygen, with a small and varying quantity of carbonic acid gas. 

 We are first struck with the differing proportion of the nitrogen 

 gas found in this water 97 to 3, whereas in rain water the pro- 



