REPORT OF THE CHEMIST. 



149 



of compensation is complete iiud absolutely perfect till man interposes 

 his arrangements to break up the harmony of nature, by placing the 

 wastes of animal life beyond the reach of the organizing forces which 

 Avould economize theui in the ever-recurring circle of life. 



Few persons think how seriously the important question of food-supply 

 is aifected by the waste of excrement in our cities and towns. This, of 

 course, will vary som-ewhat with the quality of the food on which the 

 ])opulation subsists, but a general estimate of value may ;be made from 

 the observations of Baron Liebig, Professors Way, Hoffman, Boussin- 

 gault, &c. From these authorities, English writers have generally con- 

 curred in an estimate of 10s. ($2.30) per head as the annual value of the 

 ammonia, i^hosphoric acid, and potash contained in the solid and liquid 

 excrement of an adult, or Ss. ($1.81) per head for the whole population. 

 This valuation is based on a number of analyses of solid and liquid ex- 

 crement in the usual proportions, which give an average in 100 parts — 



This table reveals the fact that if human excrement was deprived 

 of its water, the dry residuum would contain as high a percentage of 

 ammonia as the best specimen of Peruvian guano. It would also be but 

 little inferior to guano in the imi)ortant element of phosphoric acid. At 

 the estimated prices of ammonia and phosphoric acid, this table will 

 give a much higher value to excrement than that named above ; but 

 the difficulty of collecting all the wastes of a city, and the almost un- 

 avoidable loss of ammonia in the evaporation of the crude mass to a 

 convenient state of dryness, have reduced the j)ractical value to the 

 English standard of 8s. per individual of the whole population. It 

 must be remembered, however, that this is an estimate of what might 

 be saved by utilizing this single waste, and not the amount actually lost 

 in the sewage of cities. But even at the low estimate we have made of 

 this single item of waste, the loss to a city of 100,000 inhabitants would 

 amount to $184,000 per annum. 



Professor Voelcker estimates that the use of 280 pounds of guano on 

 an acre of land gives on an average an increase of twelve bushels of 

 grain. At the same rate the excreta of an adult for one year, if applied 

 to an acre of ground, will furnish the elements for at least ten bushels 

 of wheat. It will really contain the ammonia and iDhosphoric acid for 

 one hundred pounds of wheat, though in potash, lime, and magnesia it 

 will fall short. 



From this stand-point we may begin to realize the magnitude of this 

 loss, and can calculate, with a good degree of certainty, its ultimate 

 consequences. It is but fair, however, to say that all this is not abso- 

 lute loss. A large proportion of the nitrogen contained in sewage and 

 in the contents of cess-pools and j)rivy- vaults is converted into ammo- 

 nia, which, in the gaseous state, escapes into the air, to be washed out 



