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containing any acid matter. It forms the greatest 

 part of calcined bones. It exists in most excremen- 

 titious substances, and is found both in the straw and 

 grain of wheat, barley r oats and rye, and likewise in 

 beans, peas and tares. It exists in some places in 

 these islands native; but only in very small quantities. 

 Phosphate of lime is generally conveyed to the land in 

 the composition of other manure; and it is probably 

 necessary to corn crops and other white crops. 



Bone ashes ground to powder will probably be 

 found useful on arable lands containing much vegeta- 

 ble matter; and may perhaps enable soft peats to pro- 

 duce wheat; but the powdered bone in an uncalcined 

 state is much to be preferred in all cases when it can 

 be procured. 



The Saline compounds of magnesia will require 

 very little discussion as to their uses as manures. 

 The most important relations of this subject to agri- 

 culture have been considered in the former part of 

 this Lecture, when the application of the magnesian 

 limestone was examined. In combination with sul- 

 phuric acid magnesia forms a soluble salt. This sub- 

 stance, it is stated by some enquirers, has beeen found 

 of use as a manure; but.it is not found in nature in suf- 

 ficient abundance, nor is it capable of being made ar- 

 tificially sufficiently cheap to be of useful application in 

 the common course of husbandry. 



Wood ashes consist principally of the vegetable 

 alkali united to carbonic acid; and as this alkali is 

 found in almost all plants, it is not difficult to con- 

 ceive that it may form an essential part of their or- 



