IN THE MUD OF THE LEVANT. lOl 



That springs possessing a solvent power exist, 

 is proved by their prevalence in most limestone 

 districts, producing Travertins and Tufas, but 

 more especially in volcanic regions. These 

 Tufas are apparently formed at the expense 

 of the older calcareous strata. It is also 

 evident that currents charged with solvent gas 

 may pervade individual strata for a long series 

 of ages, and eventually rob them of all their 

 lime, without materially affecting the rocks either 

 above or below. A thin parting of clay may 

 suffice to direct individual currents, and cause 

 them to flow in one direction with amazing 

 constancy for a long time. This is shewn by 

 many mineral springs, and especially by those of 

 Harrogate. In the garden of the Crown Inn, 

 springs respectively charged with sulphuretted 

 hydrogen and iron bubble up clear and sparkling, 

 within a few feet of each other, and have done so 

 for an indefinite period. Similar phenomena exist 



acting under various circumstances of heat and pressure, both 

 of which have clearly exercised a powerful modifying influence. 

 The consolidation of the Irish Chalk, as compared with that 

 of England, owing to the superincumbent mass of ancient 

 Trap, is an illustration of these latter modifying causes. The 

 degree of saturation of the calcareous fluid would also have 

 some influence over tlic result. 



