130 Observations on Liehig's " Organic Chemistry." 



from 69 to 75 per cent. Human faeces, analysed by Berzelius, 

 contain 75 per cent of water, from l| to 5 per cent of nitrogen, 

 and 15 per cent of phosphates of lime and magnesia. The 

 vegetable constituents are of influence, as they furnish carbonic 

 acid to the young plants. The quantity, however, is not great, 

 he says, and estimates it only at 5*8 per cent, the greatest be- 

 nefit being derived from the inorganic constituents. In manur- 

 ing with cow and sheep dung, we replace silicate of potash and 

 phosphates; with human faeces, phosphates of lime, and mag- 

 nesia ; with those of the horse, phosphate of magnesia and 

 silicate of potash. In the straw litter we add silicate of 

 potash and phosphates ; which, if the straw be putrefied, 

 will be in the same condition as when taken up by the ori- 

 ginal wheat or oats. The soil of a field will therefore alter 

 little, he adds, if we collect and distribute the dung carefully. 

 The phosphates carried off by men and animals will accumulate 

 in the neighbourhood of large towns. This must be compen- 

 sated for at a distance from towns by letting lie in grass ; and 

 near towns by the excrements collected, and by the ashes of the 

 wood used in houses for fuel, which also replace phosphates. 



We could keep our fields fertile, by replacing what is taken off; 

 but, when we wish to increase produce, we must add more than 

 we take away. In Flanders this is done, he says, by covering the 

 fields with ashes of wood, either lixiviated or not, and bones which 

 yield phosphates of lime and magnesia. These ashes, he says, are^ 

 often carried from eighteen to twenty- four miles. The ashes of 

 oaks yield only traces of phosphates ; those of beech 20 per cent; 

 those of the pine and fir 9 to 15 per cent, some pines much less. 

 Every 100 lb. of the lixiviated ashes of beech, he calculates, 

 would furnish as much phosphate as 460 lb. of human excre- 

 ment. 100 lb. of the ashes of the grain of wheat yield 76*5 per 

 cent of phosphates, and the straw 11-5 per cent. Hence, with 

 every 100 lb. of the ashes of the beech, we supply a field with 

 phosphates sufficient for 3,820 lb. of straw, as there are only 4*3 

 percent of ashes in the straw; and 15,000 to 18,000 lb. of corn, 

 as the ashes in it amount only to 1*3 per cent. Bones formed 

 by animals from the eating of hay, straw, and corn, yield, ac- 

 cording to an analysis of Berzelius, 55 per cent of the phosphate 

 of lime and magnesia; and, calculating that hay contains as much 

 phosphates as wheat straw, 8 lb. of bones will supply phosphates 

 to 1,000 1b. of straw, and 2 lb. to 1,000 lb. of grain. Now, 40 lb. 

 of bone dust, he calculates, are sufficient to supply three crops of 

 wheat, clover, potatoes, and turnips on an acre, with phosphates. 

 The more finely the bones are powdered, and the more intimately 

 they are mixed with the soil, the more easily are they assimilated. 

 The best way to effect the renovation, he says, is to pour over 

 the bones, in a state of fine powder, half their wcigiit of sul- 



