244 PERUVIAN GUANO, ETC. [chap. 



the average composition of human excreta, and for 

 the average yearly output of each individual, from 

 which it will be seen that neither urine nor faeces are 

 particularly rich fertilisers. 



These are mean figures for all ages, and the weights 

 of nitrogen and phosphoric acid excreted per annum 

 are calculated upon a somewhat different basis ; for 

 adults the quantities should be at least half as large 

 again. But taking high average figures, an adult only 

 excretes during a year about 12 lb. of nitrogen, 7 of 

 phosphoric acid, and 5 of potash, worth respectively 

 about 7s. 6d., 2s., and is., or los. 6d. a year in all when 

 converted into a marketable fertiliser. Though for a 

 large population the total waste may thus seem to be 

 enormous, los. 6d. per head is yet but a small amount 

 to be set against the expense of dealing with such 

 a quantity of low grade material so difficult to 

 handle. 



Many attempts have naturally been made to utilise 

 the fertilising material contained in human excreta ; on 

 the crowded lands of China it is applied fresh to the soil 

 and is daily fetched by hand from the cities for that 

 purpose, but such a mode of dealing with night soil is 

 only possible with an excessively low standard of living. 

 In the towns of Flanders and the north of France it 

 was the custom to collect the excreta in large tanks, 

 and after fermentation, to cart them out in a liquid form 

 to the fields, though modern views on public health are 

 rapidly getting rid of such practices. Almost the only 

 method of getting human excreta back to the land 

 cheaply and inoffensively is in houses or small com- 

 munities where the " earth closet " system prevails. 

 There the excreta are mixed with dry sifted earth, 

 which deodorises them quickly and completely, the 

 mixture is removed daily to a heap under cover, and 



