64 JOURNAL OF THE^ROYAL HORTICULTURAL SOCIETY. 



can be fairly estimated. The method consists in summing up in 

 B mixed manure the value of each constituent — nitrogen, phos- 

 phoric acid, and potash — from the value of these substances as 

 they can be bought in an unmixed condition. For example, 

 nitrate of soda contains about 16 per cent, of nitrogen, and can 

 be bought at £8 per ton ; it follows, therefore, that in nitrate of 

 soda of a ton (or 1 per cent.) of nitrogen, costs 10s., since 

 there is nothing else of value in the nitrate of soda. 



Again, basic slag, containing 17 per cent, of phosphoric acid, 

 can be bought for £2. 5s. per ton, so that we can allow 45s. 

 divided by 17=2s. del., for the value of ^ of a ton of phos- 

 phoric acid ; if the phosphoric acid is in a soluble condition it 

 will be wortji 4s. for the of a ton, since superphosphate 

 containing 1^ per eent. of soluble phosphoric acid costs about 

 £2. 10s. ; lastly we can estimate r Jo ton of potash to be worth 

 about 4s., since kainit, with 11 to 12 per cent, of potash, costs 

 about £2. 5s. 



Taking these values and the analysis of the first manure on 

 our list (which is one of those most widely used by gardeners), 

 \\ « see that it contains 4*7 per cent, of nitrogen ; in one ton of 

 the manure there is therefore 4*7 hundredths of a ton of nitrogen 

 worth 4*7 x 10s. =£2. 7s. ; the insoluble phosphoric acid amounts 

 to 7*5 hundredths, worth 7'5 x 2s. 9d.=£l. 0s. l\d., and as 

 there is no potash or soluble phosphoric acid present the total 

 value of one ton of the manure is £3. 7s. Ihd., instead of the 

 £20 or so for which it is sold. 



The last three manures are unmixed manures that can 

 be obtained at the present time from any merchant for about 

 the prices mentioned for lots of one ton or more ; of course for 

 smaller quantities a somewhat higher price must be paid, but 

 not to the inordinate extent demanded in the mixtures commonly 

 sold. As in two cases the valuation is greater than the price, it 

 is evident that the price taken for nitrogen, phosphoric acid, and 

 potash in all the valuations is not unfair. In the table one 

 manure stands out as an honourable exception (No. 6), which, 

 on account of the almost complete solubility of all its constituents 

 and its high degree of purity and concentration, is well worth 

 the money asked for it. 



In the table no mention is made of a further class of 

 so-called silicate and slag manures, which contain no appreciable 



