^57 



only a small per centage in the composition of the strata. 

 The most pure Carbonate of Lime is the statuary marble, 

 and the clear calcareous spars ; but in the common form, 

 as used for agriculture, and for cements, it is generally 

 combined with an appreciable quantity of silex and alumina 

 and often coloured by its containing a small portion of iron. 

 Lime, when in the state of a carbonate, is insoluble in 

 pure water, but if the water contain carbonic acid, (which 

 is generally the case with that issuing from springs,) then 

 it possesses the power of dissolving a small portion. It 

 is, however, a curious circumstance, that this capability is 

 greater at the common temperature of the atmosphere, 

 than when of greater heat. This is the reason why sedi- 

 ment occurs in boilers in which water, holding carbonate 

 of Lime in solution, is used, as the carbonic acid is dispelled 

 by the heat, the absence of which incapacitates the water 

 from any longer retaining the Lime. To shew a specimen 

 of water containing Lime, I have brought a small quantity 

 from a pump which we have on our premises at Overton, 

 to which, if I add a few drops of oxalate of ammonia, 

 (which is a delicate test of the presence of Lime,) you 

 will observe an immediate precipitate.* 



Lime is such an all-pervading substance in the different 

 strata of the earth, that few springs are devoid of it, in 

 one compound state or other, but generally as the carbonate, 

 sulphate, or muriate. In the case of the Overton water it 

 is the latter, (muriate), as the introduction of a little nitrate 

 of silver will shew, which is the test for the presence of 

 muriatic acid, and which will give the water a muddy bluish 

 tinge, increasing in darkness by exposure to the atmosphere 

 for a few minutes.f The Halifax water is, I believe, freer 



* On the introduction of a solution of oxalate of ammonia, the wafer 

 instantly gave a white precipitate. 



+ Here the addition of a few drops of a solution of nitrate of silver 

 produced the effect mentioned. 



