Relative Value and Manurial Properties of PurcJiased Food. 655 



portion of tlie nitrogen in food will also probably escape by exhalation 

 from tlie lungs and the skin. Very little of tlie nitrogen of food is, 

 however, lost by fermentation, or is necessarily lost in the keeping 

 of farmyard-manm'e ; the mineral matters, excepting a small fraction 

 only of the total amount of food, pass entirely into the excrements. 



Of the vai'ions mineral constituents of food we have only to consider 

 two, namely, potash and phosphoric acid. In estimating the fertilising 

 value of food constituents that pass into tho dung, we have therefore 

 to deal with: ^'1) nitrogen (estimated as ammonia); (2) potash ; and 

 (3) phosphoric acid. By ascertaining how much of each of these 

 matters j)asses through the animal, a very close estimate may be formed 

 of the money value of the dung produced by different articles of food. 

 Mr. Lawes, in a very valuable paper published in the year 1862, gives 

 the average composition of the priacipal kinds of food ; and from the 

 average composition, by making the proper deductions for loss of 

 nitrogen, the value of the food constituents which pass into the dung- 

 may be estimated with tolerable accuracy. Indeed Mr. Lawes made 

 such an estimate in a circular which he j)ublished some time ago. At 

 that time, however, ammonia was much more expensive, and phos- 

 phoric acid cheaper ; potash has been cheaper since the discovery 

 of the mines in Saxony. The money estimates given by Mr. Lawes 

 are based on the prices cui-rent in the year 1862 : ammonia being 

 estimated at ^d. a lb. ; phosphoric acid, calculated as phosphate of 

 lime, at Id. a lb. ; and potash at 2d. a lb. In the following estimates I 

 have calculated ammonia at 6(?. a lb. ; phosphate of lime at Ihd. a lb., 

 or one-half more than Mr. Lawes' estimate ; and jiotash at lie?, a lb., 

 or one-fourth less : these prices agreeing better with the money value 

 at which other fertilising constituents can now be purchased in the 

 manure market. 



Adopting the data which I have found in various publications, 

 many of which have been carefully collated by Mr. Lawes, I have 

 calculated the value of excrementitious matter from one ton of food 

 consumed, and I find that linseed-cake is worth as a fertiliser alone, 

 making an allowance for loss, 3/. 15s. 8r?. a ton, or somewhat less than 

 the estimate of Mr. Lawes, who puts it above 4Z. ; whilst linseed, which 

 I estimate at about 10s. a ton lower than Mr. Lawes did, is worth 

 as a fertiliser only 2L 17s. 9fZ. a ton — a point which ought to be con- 

 sidered in estimating the relative value of the cake and seed as feeding 

 materials. Decorticated cotton is worth as a fertiliser 5Z. 6s. Qtd. a 

 ton, according to my rates of charge, which are certainly not too high. 

 The ordinary English cotton-cake contains little more than one-haK 

 the amoimt of nitrogen contained in cake made from the shelled seed ; 

 it is also much poorer in phosphate of lime, and is worth only 2Z. 18s. 

 a ton. At the present selling prices of English cotton-cake, it is, 

 in my opinion, by no means a cheap food, being much dearer in 

 proportion than decorticated cotton-cake. The manurial value of 

 earthnut-cake, decorticated, is 4/. 18s. a ton, imdecorticated 2?. 10s. a ton. 

 Eape-cake, which possesses even a greater fertilising value than linseed- 

 cake, is worth, according to my estimate, 4Z. 8s. 9c7. a ton. Beans, 

 X^eas, and lentils are worth 8Z. 2s. a ton. All the leguminous seeds 



