VEGETABLE MANURLS. If) 3 



2oo. Two specimens of shell-sand from the county of 

 Donegal, lately examined, were found to possess the following 

 composition : — 



Rathmullan. Melmore, Mulroy Bay. 



Carbonate of Lime 74*40 64-36 



of Magnesia .... 0-69 3-78 



Oxide of Iron and Alumina 1 -30 0-36 



Phosphate of Lime 



Organic matter 5*10 5*66 



Sand and Siliceous matter 16*60 35*36 



Water 1*50 0*56 



99*59 99-98 



On the coasts of France, shell-sand is much valued, and is 

 applied to the land at the rate of 10 to 15 tons per acre. In 

 addition to the large amount of carbonate of lime and other 

 useful ingredients which it usually contains, Boussingault 

 calculates that 100 tons of it would convey to the soil as 

 much nitrogen (derived from the animal matter) as 32 J tons 

 of farm-yard manure. 



256. Coral- sand. — This substance, which is procured in 

 large quantities by the fishermen on the south coast of Ire- 

 land, affords the farmer another valuable source of lime. It 

 resembles shell-sand in its fertilizing qualities, but contains a 

 larger amount of animal matter, and being therefore richer in 

 nitrogen, will prove more immediately active. 



257. Phosphate of Lime. — I have already explained to 

 you that bones (199) owe much of their fertilizing qualities 

 to the compounds of phosphoric acid which they contain. By 

 referring to the table, at p. 99, you may observe that that 

 acid is an essential ingredient of all the plants which you 

 cultivate, and is especially required for the production of those 

 parts of your crops valuable for food. It exists in exceedingly 

 minute quantities in even the most fertile soils, and every 

 means of obtaining supplies of it must, therefore, be of great 

 importance to agiiculture. Some years ago, great interest 

 was excited by the discovery, in Spain, of a mineral called 

 apatite, which contained so much as 37 per cent of phosphoric 

 acid ; and recently, considerable attention has been directed 

 to the discovery of Professor Henslow, that in certain rocks 

 in Suffolk and Essex, there exist beds of water-worn nodules, 

 which have been termed coj)rolites* containing so much as 



* These curious nodules are supposed by geologists to be the fossil 

 dung of extinct animals. 







