328 



EECEEATIVE SCIENCE. 



to sucli, but are found in all kinds of situa- 

 tions and of very high, temperatures in sites 

 remote from volcanic influence. Nor do 

 ■we find, as we could not fail to do if they 

 existed, any traces in these thermal waters of 

 chemical ingredients, such as would in them- 

 selves give rise to heat, nor, indeed, of any 

 that might result from decompositions which 

 had already given rise to an elevation of tem- 

 perature. Witness the waters of Naters, 

 North Wales, which rise at a temperature of 

 58" Fahrenheit ; those at Leuck at 72^ ; of 

 Bagnes at Lavey, near Bex, at 65" ; Sante 

 de Pucelle, at Chamouni, and St. Gervaise, 

 on Mont Blanc, both registering 52' or 53' ; 

 Cormayeur and St. Didier, on the southern 

 declivity of Mont Blanc, at 50" ; and those 

 at Aix-les-Bains, in Savoy, at 70" to 72". All 

 these springs are noted for the comparative 

 purity of their waters, and the steadiness of 

 their temperature, without regard to the vi- 

 cissitudes of the seasons, and in each case the 

 relative temperature is in proportion to the 

 distance of the fountain from the basal 

 granite. 



At Carlsbad the springs have a tem- 

 perature of 165" Fahrenheit, or nearly double 

 the warmth of the human body, and none 

 of the ingredients which the water yields, 

 on analysis, account in any way for its 

 heat. At Aix-la-Chapelle, the waters rise 

 at 143'; at Bath, at 114"; and in both 

 instances the sources of the supply are 

 near, or upon, primitive beds of granite. 

 Most mineral waters contain lime, common 

 salt, potash, minute proportions of sulphates 

 and phosphates, and large quantities of car- 

 bonic acid ; and of these the lime is the only 

 one which could give rise to heat. But any 

 one acquainted with chemistry must see at a 

 glance that lime is not the cause ; for, if it 

 were, the waters would rise at boiling heat, 

 or but a few degrees below it, whereas the 

 warmest of thermal springs, excepting, of 

 course, such remarkable examples as the 

 Geysers, which are true aqueous volcanoes, 



do not rise beyond a point at least 50" 

 under boiling heat. 



Wherever we penetrate the crust of the 

 earth, increase of temperature accompanies 

 increase of depth. Mining, quarrying, and 

 boring operations offer the best possible op- 

 portunities for the determination of this rate 

 of increase. In the Artesian well at G-ren- 

 elle, the temperature is equal to 84' Fahren- 

 heit, at a depth of 1230 feet, and this in win- 

 ter, when the air at the surface is not higher 

 than 28' or 30'. Mr. Fox, of the United 

 Mines, in Cornwall, has furnished some inte- 

 resting details of the increase of temperature 

 downwards indicated by the springs of those 

 mines. The mine of Gwennap, which yields 

 abundance of copper ore, has a vast number 

 of warm springs ; one of these, which rises at 

 a depth of 200 fathoms below the level of the 

 sea, discharges 94 gallons a minute, at a tem- 

 perature of 106^" Fahrenheit, while, on the 

 other side, is a spring which discharges 30 

 gallons a minute at the temperature of 971" 

 Fahrenheit. The air near both these springs 

 was found to be at 104|", and the highest 

 temperature of the air hitherto experienced 

 106'. Nor are such thermal fountains scarce. 

 They abound in every region of the globe, 

 show everywhere an affinity for granite, and 

 have a regular increase of temperature propor- 

 tionate to the increase in the depth of their 

 source. 



But the most specific, because utterly re- 

 moved from the region of partial influences, 

 is the argument deduced from cosmical phe- 

 nomena ; the figure of the earth, the motions 

 of the moon, the comparative amounts of heat 

 radiated from the sun, and the observed 

 temperature of the earth. There is scarcely 

 any one of the great propositions in Astro- 

 nomy but may be made directly or indirectly 

 to illustrate this problem of internal heat. 



Had the earth been solid when it first 

 began to rotate on its axis, it must necessarily 

 have preserved to the present day its original 

 figure, notwithstanding its rotary motion. 



