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gree. And one of the most fertile parts of Cornwall, 

 the Lizard, is a district in which the soil contains 

 mild magnesian earth. 



The Lizard Downs bear a short and green grass, 

 which feeds sheep producing excellent mutton ; and 

 the cultivated parts are amongst the best corn lands in 

 the county. 



That the theory which I have ventured to give of 

 the operation of magnesian lime is not unfounded, is 

 shewn by an experiment which I made expressly for 

 the purpose of determining the true nature of the 

 operation of this substance. I took four portions of 

 the same soil : with one I mixed 20 of its weight of 

 caustic magnesia, with another I mixed the same 

 quantity of magnesia and a proportion of a fat decom- 

 posing peat equal to one-fourth of the weight of the 

 soil. One portion of soil remained in its natural 

 state : and another was mixed with peat without mag- 

 nesia. The mixtures were made in December 1 806 ; 

 and in April 1807, barley was sown in all of them. 

 It grew very well in the pure soil ; but better in the 

 soil containing the magnesia and peat ; and nearly as 

 well in the soil containing peat alone : but in the soil 

 containing the magnesia alone, it rose very feeble, and 

 looked yellow and sickly. 



I repeated this experiment in the summer of 1810 

 with similar results ; and I found that the magnesia 

 in the soil mixed with peat became strongly efferves- 

 cent, whilst the portion in the unmixed soil gave car- 

 bonic acid in much smaller quantities. In the one case 

 the magnesia had assisted in the formation of a man- 



p 2 



