OF ARTIFICIAL MANURES. l47 



sisted wliolly of this mineral matter. Among-st these, gyp- 

 sum was much used, which was entirely a mineral manure, 

 consisting- of sulphuric acid and lime, common sulphate of 

 soda, and other substances. But tliere were mixtures of 

 those substances, and those mixtures were now used very 

 extensively. There was also a class of artificial manures, 

 which contained what he mig-ht call combustible or org-anic 

 matter, which could be consumed or burned. The manure 

 used in fertilizing- g-round very frequently contained a por- 

 tion of tliis org-anic matter, which was of g-reat value in the 

 g-rowth of plants, and which he would by-and-by explain. 

 Among-st those manures, so extensively used of late were, ox- 

 hones, which were composed of the following- substances, — 



Cartilage 33-3 



Phosphate of lime 57 '4 



Phosphate of magnesia 2-0 



Carbonate of lime 3-9 



Soda, with a little common salt 3-4 



100 



Now 30 per cent, of this matter burned, wliile the rest was 

 not consumable. Eape-dust was extensively used as manure, 

 and contained a large proportion of org-anic matter, for when 

 it was burned it left a residimm of 8 or 10 per cent, of 

 mineral matter. Another substance — g-uano — which was 

 the dropi)ing's of birds, when burned, left a larg-e proportion 

 of mineral matter, and was a verj^ useful manure, if applied 

 in proper time, in proper quantities, and imder right condi- 

 tions. These substances were more or less natural manures ; 

 but now they had received, in consequence of the researches 

 made — long and laboriously made — into the composition of 

 plants, and soils, and minerals, a knowledge of what a given 

 soil required to grow a given crop. They were, therefore, 

 enabled to make artificial mixtures of what the soil required 

 to grow a given crop, and he considered this most imi)ortant 

 in the present transition state of their agriculture. The 

 farmer being by this means, to a certain extent, enabled to 

 turn the old elements, which were formerly the opponents of 

 his prosperity, into the most beneficial instruments for his 

 service. The principle was this : — If they took a given 

 plant of any sort and burned it, there remained behind a 

 certain quantity of mineral matter — sometimes more and 

 sometimes less, according- to the nature of the plant. Tlie 

 principle upon which the manufacture of the substances to 



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