OF MANUttE. 



61 



mum 5 per cent. In all cases, however 

 they were richer in this element than thj 

 excrements of other animals. Berzeliu 

 obtained by the incineration of 100 parts oj 

 dried excrements, 15 parts of ashes, whic] 

 were principally composed of the phosphate, 

 of lime and magnesia. 



The following quantitative organic ana 

 lysis has recently been executed for the pur 

 pose of ascertaining the proportion of carbon 

 nitrogen, and inorganic matter contained in 

 faeces, in comparison with the food taken.* 

 (Playfair.) 



Carbon . . . 45'24 



Hydrogen . . 6 '88 



Nitrogen (average) . 4'00 



Oxygen . . . 30'30 



Ashes . . . 13-58 



The inorganic matter contained in the 

 excrements analyzed is nearly two per cent, 

 less than that found by Berzelius; but the 

 proportion always varies, according to the 

 nature of the food. 



It is quite certain that the vegetable con- 

 stituents of the excrements with which we 

 manure our fields cannot be entirely without 

 influence upon the growth of the crops on 

 them, for they will decay, and thus furnish 

 carbonic acid to the young plants. But it 

 cannot be imagined that their influence is 

 very great, when it is considered that a good 

 soil is manured only once every six or seven 

 years, or once every eleven or twelve years, 

 when sainfoin or lucerne has been raised on 

 it, that the quantity of carbon thus given to 

 the land corresponds to only 5-8 per cent, of 

 what is removed in the form of herbs, straw, 

 and grain; and farther that the rain-water 

 received by a soil contains much more car- 

 bon in the form of carbonic acid than these 

 vegetable constituents of the manure. 



The peculiar action then, of the solid ex- 

 crements is limited to their inorganic con- 

 stituents, which thus restore to a soil that 

 which is removed in the form of corn, roots, 

 or grain. When we manure land with the 

 dung of the cow or sheep, we supply it 

 with silicate of potash and some salts of 

 phosphoric acid. In human faeces we give 

 it the phosphates of lime and magnesia; 

 and in those of the horse, phosphate of 

 magnesia, and silicate of potash. In the 

 straw which has served as litter, we add a 

 farther quantity of silicate of potash and 

 phosphates ; which, if the straw be putre- 

 fied, are in exactly the same condition in 

 which they were before being assimilated. 



It is evident, therefore, that the soil of a 

 field will alter but little, if we collect and 

 distribute the dung carefully ; a certain por- 

 tion of the posphates, however, must be lost 

 every year, being removed from the land 



* The details of the analysis are as follows : 

 2-356 grammes left 0'320 gramme ashes after 

 incineration ; these consisted of the phosphate of 

 lime and magnesia. 0'352 gramme yielded, on 

 combustion with oxide of copper, 0'576 gram, 

 carbonic acid, and 0'218 gram, water. (L. P.) 



with the corn and cattle, and this portion 

 will accumulate in the neighbourhood of 

 large towns. The loss thus suffered must 

 be compensated for in a well-managed farm, 

 and this is partly done by allowing the fields 

 to lie in grass. In Germany, it is considered 

 that for every 100 acres of corn-land, there 

 must, in order to effect a profitable cultiva- 

 tion, be 20 acres of pasture-land, which pro- 

 duce annually, on an average, 500 Ibs. of 

 hay. Now, assuming that the ashes of the 

 excrements of the animals fed with this hay 

 amount to 6.82 per cent., then 341 Ibs. of 

 the silicate of lime and posphates of magne- 

 sia and lime must be yielded by these excre- 

 ments, and will in a certain measure com- 

 pensate for the loss which the corn-land had 

 sustained. 



The absolute loss in the salts of phospho- 

 ric acid, which are not again replaced, is 

 spread over so great an extent of surface, 

 that it scarcely deserves to be taken ac- 

 count of. But the loss of phosphates is 

 again replaced in the pastures by the ashes 

 of the wood used in our houses for fuel. 



We could keep our fields in a constant 

 state of fertility by replacing every year as 

 mach as we remove from them in the form 

 of produce; but an increase of fertility, and 

 consequent increase of crop, can only be 

 obtained when we add more to them than 

 we take away. It will be found, that of two 

 fields placed under conditions otherwise 

 similar, the one will be most fruitful upon 

 which the plants are enabled to appropriate 

 more easily and in greater abundance those 

 contents of the soil which are essential to 

 their growth and developement. 



From the foregoing remarks it will readily 

 inferred, that for animal excrements, 

 other substances containing their essential 

 constituents may be substituted. In Flan- 

 ders, the yearly loss of the necessaiy matters 

 'n the soil is completely restored by covering 

 he fields with ashes of wood 'or bones, 

 which may or may not have been lixiviated^ 

 and of which the greatest part consists ot 

 he phosphates of lime and magnesia. The 

 jreat importance of manuring with ashes 

 las been long recognised by agriculturists 

 as the result of experience. So great a 

 value, indeed, is attached to this material in 

 he vicinity of Marburg and in the Wette- 

 au,* that it is transported as a manure 

 rom the distance of 18 or 24 miles. Its use 

 will be at once perceived, when it is con- 

 idered that the ashes, after having been 

 cashed with water, contain silicate of pot 

 sh exactly in the same proportion as in 

 traw HO Si O 3 -f K O.,) and that their 

 >nly other constituents are salts of phospho- 

 ic acid. 



But ashes obtained from various kinds of 

 rees are of very unequal value for this pur- 

 ose; those from oak-wood are the least, 



* Two well-known agricultural districts ; the 

 rst in Hesse-Cassel, the second in Hesse-Darm- 

 tadt. 



F 



