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or for the purpose of preventing noxious effluvia, as 

 in certain cases mentioned in the last Lecture. It is 

 injurious when mixed with any common dung, and 

 tends to render the extractive matter insoluble. 



I made an experiment on this subject : I mixed 

 a quantity of the brown soluble extract, which was 

 procured from sheeps' dung with five times its weight 

 of quicklime. I then moistened them with water ; 

 the mixture heated very much ; it was suffered to re- 

 main for 14 hours, and was then acted on by six or 

 seven times its bulk of pure water : the water, after 

 being passed through a filter, was evaporated to dry* 

 ness ; the solid matter obtained was scarcely coloured, 

 and was lime mixed with a little saline matter* 



In those cases in which fermentation is useful to 

 produce nutriment from vegetable substances, lime is 

 always efficacious. I mixed some moist tanner's spent 

 bark with one-fifth of its weight of quicklime, and suf- 

 fered them to remain together in a close vessel for 

 three months ; the lime had become coloured and was 

 effervescent : when water was boiled upon the mix- 

 ture it gained a tint of fawn colour, and by evapora- 

 tion furnished a fawn-coloured powder, which must 

 have consisted of lime united to vegetable matter, for 

 it burnt when stongly heated and left a residuum of 

 mild lime. 



The limestones containing alumina and silica are 

 less fitted for the purposes of manure than pure lime- 

 stones ; but the lime formed from them has no nox- 

 ious quality. Such stones are less efficacious, merely 

 because they furnish a smaller quantity of quicklime* 



