Sir J. Sinclair says, "If a few spoonfuls of milk are left in the udder of the cow at milking; if any of the implements used in the dairy are allowed to be tainted by neglect; if the dairy-house be kept dirty, or out of order; if the milk is either too hot or too cold at coagulation; if too much or too little rennet is put into the milk; if the whey is not speedily taken off; if too much or too little salt is applied; if butter is too slowly or too hastily churned; or if other minute attentions are neglected, the milk will be in a great measure lost. If these nice operations occurred once a month, or once a week, they might be easily guarded against; but as they require to be observed during every stage of the process, and almost every hour of the day, the most vigilant attention must be kept up during the whole season." A KNOWLEDGE OF AGRICULTURAL AND ANIMAL CHEMISTRY IMPORTANT TO FARMERS. It is a well-known fact that plants require for their germination and growth different constituents of soil, and that animals require different forms of food to build up the waste, and promote the living integrity--the vital powers. Its order to supply the materials necessary for animal and vegetable nutrition, we require alternate changes--the former in the diet, and the latter in the soil. Experience has proved that the cultivation of a plant for several successive years on the same soil impoverishes it, or the plant degenerates. On the contrary, if a piece of land be suffered to lie uncultivated for a short time, it will yield, in spite of the loss of time, a greater quantity of grain; for, during the interval of rest, the soil regains its original equilibrium. It has been satisfactorily demonstrated that a fruit-tree cannot be made to grow and bring forth good fruit on the same spot where another of the same species has stood; at least not until a lapse of years. This is a fact worth knowing, for it applies more or less to all forms of vegetation. Another fact of experience is, that some plants thrive on the same soil only after a lapse of years, while others may be cultivated in close succession, _provided the soil is kept in equilibrium by artificial means_; these are subsoiling, &c. Some kinds of plants improve the sod, while others impoverish or exhaust it. Professor Liebig tells us, "turnips, cabbages, beets, oats, and rye are considered to belong to the class which impoverish the soil; while by wheat, hops, madder, hemp, and poppies, it is supposed to be entirely exhausted." Many of our farmers expend large sums of money in the purchase of manure, with a view of improving the soil; and they suppose that their crops will be abundant in proportion to the amount of manure; yet many have discovered that, in spite of the extra expense and labor, the produce of their farms decreased.