from the magnesian limestone may be applied in 
large quantities to peats ; and that where lands 
have been injured by the application of too large 
a quantity of magnesian lime, peat will be a proper 
and efficient remedy. 
I mentioned that magnesian limestones effer- 
vesced little when plunged into an acid. A simple 
test of magnesia in a limestone is this circumstance, 
and its rendering diluted nitric acid or aqua fortis 
milky. 
From the analysis of Mr. Tennant, it appears 
that the magnesian limestones contain from 
20.3 to 22.5 magnesia. 
29.5 to 31.7 lime. 
47.2 carbonic acid. 
0.8 clay and oxide of iron. 
Magnesian limestones are usually coloured brown 
or a pale yellow. They are found in Somersetshire, 
Leicestershire, Derbyshire, Shropshire, Durham, 
and Yorkshire. I have never met with any in 
other counties in England; but they abound in 
many parts of Ireland, particularly near Belfast. 
The use of lime as a cement is not a proper sub- 
ject for extensive discussion in a course of Lectures 
on the chemistry of agriculture ; yet as the theory 
of the operation of lime in this way is not fully 
stated in any elementary book that I have perused, 
I shall say a very few words on the applications of' 
this part of chemical knowledge. 
There are two modes in which lime acts as a 
cement ; in its combination with water, and in its 
combination with carbonic acid. 
The hydrate of lime has been already mentioned. 
