[ 287 j 



I mentioned bituminous limestones. There is 

 very seldom any considerable portion of coally matter 

 in these stones ; never as much as five parts in 100 ; 

 but such limestones make very good lime. The car- 

 bonaceous matter can do no injury to the land, and 

 may, under certain circumstances, become a food of 

 the plant, as is evident from what was stated in the 

 last Lecture. 



The subject of the application of the magnesian 

 limestone is one of great interest. 



It had been long known to farmers in the neigh- 

 bourhood of Doncaster, that lime made from a certain 

 limestone applied to the land, often injured the crops 

 considerably, as I mentioned in the Introductory Lec- 

 ture. Mr. Tennant, in making a series of experi- 

 ments upon this peculiar calcareous substance, found 

 that it contained magnesia ; and on mixing some cal- 

 cined magnesia with soil, in which he sowed different 

 seeds, he found that they either died, or vegetated in 

 a very imperfect manner, and the plants were never 

 healthy. And with great justice and ingenuity he re- 

 ferred the bad effects of the peculiar limestone to the 

 magnesian earth it contains. 



In making some enquiries concerning this sub- 

 ject, I found that there were cases in which this mag- 

 nesian limestone was used with good effect. 



Amongst some specimens of limestone which 

 Lord Somerville put into my hands, two marked as 

 peculiarly good proved to be magnesian limestones. 

 And lime made from the Breedon limestone is used in 

 Leicestershire, where it is called hot lime ; and I have 



