No. 7. 



Phosphates. 



223 



lentils, we obtain ashes which are distin- 

 guished from the ashes of all other parts of 

 vegetables by the absence of alkaline car- 

 bonates. The ashes of these seeds, when 

 recently prepared, do not effervesce with 

 acids; their soluble ingredients consist solely 

 of alkaline phosphates, the insoluble parts of 

 phosphate of lime, phosphate of magnesia, and 

 oxide of iron ; consequently of the very same 

 salts which are contained in blood, and which 

 are absolutely indispensable to its formation. 

 We are thus brought to the further indis- 

 putable conclusion, that no seeds suitable to 

 become food for man and animals, can be 

 formed in any plant without the presence 

 and co-operation of the phosphates. A field 

 in which phosphate of lime or the alkaline 

 phosphates form no part of the soil, is totally 

 incapakle of producing grain, peas, or beans. 



An enormous quantity of these substances 

 indispensable to the nourishment of plants, 

 is annually withdrawn from the soil and car- 

 ried into great towns, in the shape of flour, 

 cattle, et cetera. It is certain that this in- 

 cessant removal of the phosphates must tend 

 to exhaust the land and diminish its capabil- 

 ity of producing grain. The fields of Great 

 Britain are in a state of progressive exhaust 

 ion from this cause, as is proved by the rapid 

 extension of the cultivation of turnips and 

 mangel wurzei — plants which contain the 

 least amount of the phosphates, and there 

 fore require the smallest quantity for their 

 developement. These roots contain 80 to 

 92 per cent, of water. Their great bulk 

 makes the amount of produce fallacious, as 

 respects their adaptation to the food of ani- 

 mals, inasmuch as their contents of the in- 

 gredients of the blood ; that is, of substances 

 which can be transformed into flesh — stands 

 in a direct ratio to their amojunt of phos- 

 phates, without which neither blood nor 

 flesh can be formed. 



Our fields will become more and more 

 deficient in these essential ingredients of 

 food, in all localities where custom and hab- 

 its do not admit the collection of the fluid 

 and solid excrements of man, and their ap- 

 plication to the purposes of agriculture. In 

 a former letter I showed you how great a 

 waste of phosphates is unavoidable in Eng- 

 land, and referred to the well known fact, 

 that the importation of bones restored in a 

 most admirable manner, the fertility of the 

 fields exhausted from this cause. In the 

 year 1827, the importation of bones for ma- 

 nure amounted to forty thousand tons, and 

 Huskisson estimated their value to be from 

 one hundred thousand to two hundred thou- 

 sand pounds sterling. The importation is 

 still greater at present, but it is far from 

 being sufliicient to supply the waste. 



Another proof of the efficacy of tlie phos- 

 phates in restoring fertility to exhausted 

 land, is afforded by the use of the guano — 

 a manure which, although of recent intro- 

 duction into England, has found such gene- 

 ral and extensive application. 



We believe that the importation of one 

 hundred weight of guano, is equivalent to 

 the importation of eight hundred weight of 

 wheat — the hundred weight of guano as- 

 sumes, in a time which can be accurately 

 estimated, the form of a quantity of food cor- 

 responding to eight hundred weight of wheat. 

 The same estimate is applicable in the val- 

 uation of bones. 



If it were possible to restore to the soil of 

 England and Scotland the phosphates which 

 during the last fifly years have been carried 

 to the sea by the Thames and the Clyde, it 

 would be equivalent to manuring with mil- 

 lions of hundred weights of bones, and the 

 produce of the land would increase one- 

 third, or perhaps double itself, in five to ten 

 years. 



We cannot doubt that the same result 

 would follow, if the price of the guano ad- 

 mitted the application of a quantity to the 

 surface of the fields, containing as much of 

 the phosphates as have been withdrawn from 

 them in the same period. 



If a rich and cheap source of phosphate 

 of lime and the alkaline phosphates were 

 open to England, there can be no question 

 that the importation of foreign corn might 

 be altogether dispensed with afler a short 

 time. For these materials England is at 

 present dependent upon foreign countries, 

 and the high price of guano and of bones 

 prevents their general application, and in 

 sufficient quantity. Every year the trade 

 in these substances must decrease, or their 

 price will rise as the demand for them in- 

 creases. 



According to these premises, it cannot be 

 disputed, that the annual expense of Great 

 Britain for the importation of bones and 

 guano is equivalent to a duty on corn — with 

 this difference only, that the amount is paid 

 to foreigners in money. 



To restore the disturbed equilibrium of 

 constitution of the soil — to fertilize her fields 

 England requires an enormous supply of 

 animal excrements; and it must, therefore, 

 excite considerable interest to learn that she 

 possesses, beneath her soil, beds of fossil 

 guano, strata of animal excrements, in a 

 state which will probably allow of their being 

 employed as a manure at a very small ex- 

 pense. 



The coprolites discovered by Dr. Buck- 

 land — a discovery of the highest interest to 

 geology — are these excrements; and it seems 



