74 THE WONDERS OF GEOLOGY. Lect. I. 



The former existence of limited glaciers in some parts of 

 Great Britain, perhaps accompanied with a lower clima- 

 torial temperature than now prevails, appears to me the 

 extent to which, in the present state of our knowledge, the 

 glacial theory can be admitted as a vera causa, in our 

 attempts to interpret the origin of the drift of the British 

 islands. It may, however, be well to state, that if 

 an elevation of the European continent to the amount of 

 but 2000 feet were to take place, a great part of its surface 

 would be covered with glaciers and perpetual snow, and 

 cease to be habitable. 



33. Incrtjsting springs. — The phenomena hitherto 

 considered, are referable to the mechanical action of water ; 

 and the effect has been disintegration, and destruction, 

 in the first instance, and in the second the accumulation 

 of sediments in water-courses, and their transport into 

 the bed of the sea. We must now refer to an operation 

 of a totally different character— the power possessed by 

 streams, as clear and sparkling as poet ever feigned or 

 sung, of consolidating loose materials, of converting porous 

 strata into solid stone, and of filling up their own channels 

 by the deposition of calcareous matter. 



That most fresh water holds a certain proportion of 

 carbonate of lime * in solution, is well known ; and also 

 that changes of temperature, and certain other causes, will 

 occasion the calcareous earth to be in part or wholly preci- 

 pitated. The fur, as it is called, that lines a boiler which 

 has been long in use, affords a familiar illustration of this 

 fact. At the temperature of 60°, lime is soluble in 700 

 times its weight of water, and if to the solution a small 



* Carbonate of lime consists of lime in combination with carbonic 

 acid gas, which is a most abundant natural product. This gas is 

 irrespirable, and when pure, will immediately suffocate an animal 

 immersed in it, and extinguish flame. 





