840 = 574 Influence of Chemical Discoveries on 
valuation that may be adopted by different persons may v 
but the statement that the food of fattening-stock, in pas"- 
through the animal, loses little (if any) of its nitrogen bv ex' 
tion, and none of its mineral constituents, and that, practi 
speaking, the whole of the mineral matter and about nine-ten 
of the nitrogen of the food are recovered in the dung and uri: 
of the animal, are based on carefully ascertained facts. In tl 
country, a long series of most carefully conducted and intelligent 
conceived feeding experiments have been made by jVIr. Law 
of Rothamsted. These experiments extended over several yea 
and they were carried out at great expense, with a variety 
feeding-stuffs which were given to oxen, sheep, and pigs, ca 
being taken to put up a sufficient number of fattening anim; 
to counteract the in-egularities arising from the different feedij 
capabilities of individual animals. The food consumed w 
carefully analysed, the gain in the live weight noted, and t 
loss in food by respiration ascertained ; and the amount ai 
quality of the manure produced by the consumption of vario 
foods were determined by laborious weighings and analyses. ■ 
The greater portion of the nitrogenous and mineral matt< 
of the food is recovered in the manure, and the greater p; 
of the non-nitrogenous substances is lost by respiration ai 
other exhalations, whilst a comparatively small proportion 
the nitrogenous substance and of the mineral matter of food 
retained in the increase. 
For a given amount of increase produced, oxen void more 
manure, and expend more in respiration, &c., than sheep ; a 
sheep very much more than pigs. And lastly, for a giv 
weight of dry substance consumed, oxen void more as mam 
than sheep, and sheep much more than pigs ; but oxen resp 
rather less than sheep, and sheep rather less than pigs. 
The proportions of certain constituents in a ton of varic 
articles of food which are stored up in the animal, and the pi 
portions which pass into the manure by the consumption of 
ton of different kinds of food, have thus been ascertained w 
tolerable precision by actual experiments. If, therefore, t 
composition of the various kinds of food that^ are given 
fattening-animals is known, we can determine beforehai 
without actually analysing the manure produced from the cc 
sumption of a ton of each kind, how much nitrogen, pota: 
and phosphoric acid existing in the food will be recovered in t 
manure produced. And as nitrogen (or its equivalent express 
as ammonia), potasli, and phosphoric acid (or its equival* 
expressed as phosphate of lime) have a certain market val 
as manuring constituents, we can likewise ascertain the mor 
value of the njanure produced from the consumption of a t 
