278 APPENDIX TO PART I. 



requiring, for the chemical constitution of their body, or 

 for the formation of their milk, more nitrogen, and more 

 phosphate of lime, than sheep ; whilst the latter require 

 again more sulphur, and more common salt, for the forma- 

 tion of their wool. Hence the excrements of oxen contain 

 less nitrogen than those of sheep, whilst they are more 

 abundant in salt and sulphur. 



'* Accordingly it is found in practice, that sheep's dung 

 ferments more readily than that of black cattle. ' The 

 latter, therefore,' says Liebig, 'is of most service on soils 

 consisting of lime and sand, which contain no silicate of 

 potass or phosphates, whilst their value is much less when 

 applied to soils formed of argillaceous earth, basalt, gran- 

 ite, porphyry, clinkstone, and even mountain limestone, 

 because all these contain potass in considerable quantity.' 



** Human excrements, on the contrary, are useful in 

 both descriptions of soil, but would be inadequate to supply 

 the silicate of potass which is wanting in the former. 



*'The constituents, however, to which the solid excre- 

 ments of animals in general owe their principal efficacy 

 are the earthy phosphates ; and hence we see, why it is 

 that animal manure should favor the growth of corn, which 

 contains so much phosphate of lime and magnesia, and 

 why the earth of bones, and even the ashes of certain 

 kinds of wood, such as the beech, which contain phos- 

 phates, may be advantageously substituted, whilst the ash- 

 es of others, as of the oak and fir, which are deficient in 

 the phosphates, are of very little avail. 



" We see also the cause of the fertilizing quality of 

 liquid manure, as employed in Holland, for those crops 

 which are most subservient to the nourishment of man. 



** Liquid manure consists in a great degree of the urine 

 of various animals, which, during its decomposition, exhales 

 a larger quantity of ammonia than any other species of 

 excrement. 



" Now all kinds of corn contain nitrogen, and conse- 

 quently any manure which yields a ready supply of ammo- 

 nia, must cause a fuller development of those parts of the 

 plant which are of the greatest use to man. 



*'Even the kind of animal manure usually employed in 

 this country owes its efficacy, so far as it is dependent 

 upon the ammonia present, to the urine, rather than to the 

 solid excrement, of which it is made up, and hence be- 

 comes materially deteriorated in this respect, when the 

 more liquid portions are allowed to drain off from it. 



