70 SIXTH REPORT — 1836. 



rity of Laplace, and has also received the support of many mo- 

 dern naturalists. 



Professor Bischof *, in adopting it, has undertaken in a late 

 paper first of all to i-efute the opposite hypothesis, but in at- 

 tempting so to do, has, I conceive, mistaken the views of its ad- 

 vocates. 



Thus he quotes an experiment of his own, in which the com- 

 bustion of 15 grains of sodium, in water containing a quantity of 

 sulphuric and muriatic acid, such as would be adequate to form 

 the saline matter present in a particular thermal spring, raised 

 the temperature of 1000 grains of water scarcely 3° ; and this 

 he alleges as a proof, that the heat cannot have arisen from any 

 process of oxidation in which sodium acts a part. 



But under either view of the subject, the increased tempera- 

 ture of the spring must be attributed to that of the contiguous 

 rocks, the only question being, do these rocks derive their high 

 temperature from a central fluid mass, or from chemical pi"0- 

 cesses taking place generally in the interior of the globe ? 



Having discussed this question at length elsewhere, I will at 

 present confine myself to remarking, that the supporters of Bi- 

 schof 's views ought to be able to explain to us, why thermal springs 

 are of local occurrence, and most frequent in proportion to the 

 frequency of other indications of igneous activity; and if these 

 latter indications are assumed to be themselves nothing more, 

 than the result of the contraction of the earth's crust upon its 

 internal fluid contents, why that contraction should be always 

 accompanied with those exertions of explosive energy which we 

 witness in volcanos, and those emissions of gas which are com- 

 mon to both. 



They should also explain to us, why primary rocks, traversed 

 as they so frequently are with fissures of all descriptions, should 

 not in every part of the woi-ld, and in every kind of situation, give 

 rise to hot springs, by evolving steam from their interior, and 

 why they never appear to give issue to that class of thermal 

 waters, which I have noticed in Ischia as being unaccompanied 

 with gaseous products, and which therefore I suppose, to be 

 purely the result of the infiltration of water to spots in the in- 

 terior of the earth retaining a high temperatvue. 



In order however duly to appreciate the degree of support, 

 which the chemical theory of thermal waters appears to derive 

 from the nature of the gases which accompany them, I shall 

 next propose to consider in detail the manner, in which these 

 clastic fluids may severally be supposed to have been generated. 



* Erliiibiiirjh Fhi/. Joiinial for April 1836. 



