Natural History of Volcanos and Earthquakes. 69 



It is possible that the raising and fracture of the secondary 

 strata in such valleys of elevation, was the consequence of the 

 elevation of volcanic masses from beneath, which masses have 

 not appeared at the surface. Supposing this to be the case, 

 we can easily imagine that at su^ch places, mineral springs may 

 be produced which contain carbonates of alkalies, because the 

 meteoric water only can penetrate to these masses. But the 

 low temperature of the acidulous springs in question, shows that 

 meteoric water penetrates to very small depths only at these 

 places. 



Valleys of elevation of the kind described, seem to be of tol- 

 erably frequent occurrence ; thermal springs and disengagements 

 of carbonic acid gas are not, however, always met with, either 

 for want of sufficient depth of the clefts, or for want of mate- 

 rials which give rise to the disengagement of carbonic acid gas. 

 Instances of three of such valleys at the. eastern end of the ba- 

 sin of London^ are given by Buckland.* See also his and Con- 

 ybeare'sf description of the structure of the country at St. Vm^ 

 cenfs rocks ; and the example at Matlock long ago pointed out 

 by Whitehurst.| Many other instances of this kind occur in 

 Daubeny's report. || StiirTt-^, also has long ago shown, that the 

 rocks in the neighborhood of the mineral springs of the Nassau 

 territory manifest evident changes in the direction and inclination 

 of their strata, especially saddle-shaped elevations, often accom- 

 panied with fractures. 



Finally, dislocations or faults produced by elevations and 

 intersecting stratified rocks, may direct the subterranean coursa 

 of springs in a very diiferent manner. BucklandIT has given 

 many instances of springs originating from causes of this kind. 



If we take a summary view of all that has been said on the 

 subject of thermal springs, we shall find it impossible to avoid 

 recognizing a relation between elevations of Plutonic masses, the 

 upraising of Neptunian formations, and thermal springs. Cause 

 and effect have, however, been frequently confounded here. 

 Thermal and mineral springs are seldom, perhaps never, the cause 

 of those effects. Where, however, these effects are observed, 



* Geological Transact, sec. ser. vol. ii, parti, p. 119. t Ibid, vol. i. 



t Theory of the Earth, 1786. || P. 66. 



§ Rulhuann Wiesbaden, &c. 1823, p. 103. 

 H Geology and Mineralogy, &c, London, 1836, Vol. ii, p. 106 and 110. 



