11 



combination be, and consequently also the temperature of the 

 spring. 



Atmospheric air consists of oxygen and nitrogen, and rain 

 dissolves these gases in the proportion of one of the former to two 

 of the latter, and it is in this proportion we always find them 

 again in spi-ings. Now if the theory I have put forward be correct, 

 it will follow that whilst the oxygen has been used up in the 

 manner we have seen, the nitrogen remains uncombined and ought 

 to appear, as it does appear, in large quantities iu our hot springs, 

 which discharge daily as much as 250 cubic feet of that gas. 



A gentleman who is, I believe, a member of this club, has 

 broached the notion that the heat is due to the combustion of a 

 coal field, and thoiigh it is just possible that those mineral waters 

 which contain a veiy large amount of carbonic acid, partly owe 

 their heat to a subterranean process of combustion either of carbon 

 or carbonaceous substances by atmospheric oxygen conveyed into 

 the interior of the eartb by water, still a very slight knowledge of 

 chemistry would have satisfied him that this cannot be the case 

 with the Bath springs, on account of the absence of any notable 

 quantity of carbonic acid. 



The springs probably rise from a great depth, and if so, a gi'eat 

 deal of the heat would be due to this cause. If the permeable or 

 water-bearing strata, which supply the spring, do not crop out 

 again at the surface, but dip down under others which are 

 impervious, the water they absorb may penetrate to veiy consider- 

 able depths, and will not reappear at the surface imless it meets 

 with a fissure through which it may be forced upwards by the 

 hydrostatic pressure of the water in the upper extremity of the 

 water bearing strata. 



The rate of increase of temperature for depth varies, probably 

 according to dissimilarity in the position and inclination of the 

 strata. In the Rose Bridge Colliery, Wigan, one of the deepest, 

 if not the deepest, in the world, where the depth of 808 yards has 

 been reached, the temperature at the bottom is 93" F., giving an 

 increase of 1° F. for every 54*57 feet. 



Eveiyone must be familiar with the appearance of a chalk cliflf 

 Btudded with flints. Their occurrence and mode of formation have 



