No. 129.] 377 



The first improvement in their use consisted in fermenting them 

 with a divisor before use, so as to render them more easily solu- 

 ble for the use of plants ; other operators boiled bones in a close 

 vessel, under pressure of steam, and with very high pressure they 

 are soluble in water, and may bo added to the compost heap in 

 semi-fluid form — all the gelatine dissolving and the phosphate of 

 lime dividing readily through the fluid. The more recent im- 

 provement, however, is changing the phosphate into the super- 

 phosphate of limej and thus rendering it soluble in water, so that 

 it may be applied to the soil either in the fluid form or through 

 the compost heap. 



This change is produced by treating bones with dilute sulphuric 

 acid. The phosphate of lime is composed of phosphoric acid and 

 lime, and is not soluble in water, but when treated with sulphuric 

 acid a combination takes place between the lime and the sul- 

 phuric acid, converting part of the lime into sulphate of lime, 

 (plaster of paris) and leaving all the phosphoric acid combined 

 with part of the lime as ^uper-phosphate of lime which is soluble 

 in water and therefore is immediately absorbed by the roots ot 

 plants. 



When phosphate of lime is applied to soils fifty bushels per 

 acre is required, and ha efiects last for many years, and thus the 

 capital of the farmer is put out at compound interest, which he 

 pays himself. If the super-phosphate of lime be used, the amount 

 resulting from five bushels of bones is sufficient for an acre, and 

 the effect is much greater than when ground bones alone are used. 

 By this treatment the amount invested is readily realised at an 

 early date, and if a larger quantity be applied, as It is not vola- 

 tile, it cannot be lost but remains in the soil until the require- 

 ments of plants consume it. 



For this purpose the mercantile sulphuric acid should not 

 used, that obtained from the chamber of the manufactures, before 

 concentration, known as cAfiTnifer-adc?, is much cheaper and equal- 

 ly effective. The great expense of sulphuric acid is in its con- 

 centration, and as it requires to be diluted before use by the far- 

 mer, it should be purchased before the expense of concentration 

 has occuri-exi, 



