On Siqoerphosphate of Lime. 



231 



portions with means of sufficient aj^itation. If the proportions 

 are properly regulated and the quantity of water not too great, 

 the mixture will need no further attention, but will dry up of 

 itself: and this brings me to the subject of the mode of drying 

 up the acid compound. Some makers, after yjroducing a com- 

 pound of phosphate and acid of a semifluid or pasty character, 

 add absorbent substances to dry it into a fit state for sale. In 

 some cases they use a further quantity of the same phosphoric 

 substance for the purpose, but it is evident that it would serve the 

 same purpose to add the full amount in the first instance, pro- 

 vided sufficient means existed to produce a perfect mixture as 

 where machinery is brought into play. But when two or more 

 substances are employed, such for instance as coprolites and 

 crushed bones or animal charcoal, it is by no means indifferent 

 how the mixture is made; in that case the rule should be to add 

 the acid to that substance which is in itself and in its natural 

 state least valuable to veg-etation, and to use the more valuable 

 substances in the drying up of the mixture. 



Suppose a manufacturer intends to make superphosphate from 

 coprolite and crushed bones, and that for want of proper apparatus 

 he is necessitated to resort to the addition of one or other of these 

 substances to dry up the acid material, let him by all means add 

 the acid to the coprolite, which is comparatively valueless without 

 such treatment, and employ as his drying material the crushed 

 bones, which in their unchanged state are still most valuable 

 manures; this rule can, with requisite judgment, be applied in 

 all cases, Coprolites, whether of the crag or green sand, and 

 Spanish or American phosphates, are comparatively useless as 

 manures until they have been acted on by acid. Crushed bones, 

 animal charcoal, phosphatic-guanos, are all more or less effica- 

 cious without such treatment. If it be necessary to use one 

 phosphoric substance as the principal , and the other as the 

 accessory in the manufacture — if one is to be employed as the 

 basis and the other as a mere mechanical absorbent — let the 

 mineral phosphate be the one selected for action by the acid, and 

 the bones, guano, or animal charcoal as the substances for me- 

 chanically drying up the product. 



Mode of applying Superphosphate of Lime. — A few words on 

 the practical use of this manure will complete the present paper. 

 If the view now taken of the action of superphosphate be 

 correct — that is to say, that its efficacy consists in the production 

 in the soil of a precipitated and therefore highly comminuted 

 phosphate, and moreover of the distribution of this phosphate 

 through a large mass of soil — it follows, that to ensure its suc- 

 cessful employment the farmer must see that nothing that he does 

 to it should be opposed to either one or other of these conditions. 



