There is, doubtless, some standard of food adapted to the constitution and purposes of animals, combining with bulk a due proportion of elements of respiration, such as sugar, starch, &c., together with those of nutrition, namely, nitrogenous compounds, phosphates, and other minerals; nor can we omit oil or fat-forming substances; for, however we may be disposed to leave to philosophy the discussion as to whether sugar, starch, &c., are convertible into fat, yet I think I shall not offend the teacher of agricultural chemistry by stating that the more closely the elements of food resemble those in the animal and its product, the more efficacious will such food be for the particular purpose for which it is used. Sugar, starch, &c., vary very considerably in form and proportion from vegetable oils, which closely resemble animal fats. When we consider that plants have a two-fold function to perform,--namely, to serve as food for animals, and also for the reproduction of the like plants,--and that, after having undergone the process of digestion, they retain only one half or one third of their value as manure, the importance of affording a due but not excessive supply of each element of food essential to the wants and purposes of the animal will be evident. If we fall short, the result will be imperfect; if we supply in excess, it will entail waste and loss. Linseed and rape-cake resemble each other very closely in chemical composition; the latter is chiefly used for manure, and its price ranges usually about half that of linseed-cake. In substances poorer in nitrogen, and with more of starch, gum, oil, &c., the disparity in value as food and as manure will be proportionately greater. During the present season, Mr. Mendelsohn, of Berlin, and Mr. Gausange, who is tenant of a large royal domain near Frankfort on the Oder, on which he keeps about one hundred and fifty dairy cows, have been my visitors. These gentlemen have collected statistics in dairy countries through which they have travelled. I learned from them that in Mecklenburg, Prussia, Holland, &c., fourteen quarts of milk yield, on the average, one pound of butter; in rare instances twelve quarts are found to yield one pound. Both attach great importance to the regulation of the temperature. Mr. Mendelsohn tells me that the milk from cows fed on draff (distillers’ refuse) requires a higher temperature to induce its yield of butter than that from cows supplied with other food.