The only way in which a correct estimate of the value of linseed-cake can be arrived at is by a combined microscopical and chemical analysis; but as the feeder is not always disposed to incur the cost of this process, he should make himself acquainted with the characteristic of the genuine cake, in order to be able to discriminate, as far as possible, between it and the sophisticated article. I will indicate a few of the more prominent features of cake of excellent quality, and point out a few simple and easily-performed tests, which may serve to detect the existence of gross adulteration. Good cake is hard, of a reddish-brown color, uniform in appearance, and possesses a rather pleasant flavor and odour. The adulterated cake is commonly of a greyish hue, and has a disagreeable odour. A weighed quantity of the cake--say 100 grains--in the state of powder should be formed into a paste with an ounce of water; if it be good, the paste will be light colored, moderately stiff, and endowed with a pleasant odour and flavor. If the paste be thin, the presence of bran, or of grass seeds, is probable. The latter are easily seen through a magnifying-glass; indeed, most of them are readily recognisable by the unassisted eye: they may, therefore, be picked out, and their weight determined. Sand--a frequent adulterant--may be detected by mixing a small weighed quantity of the powdered cake with about twelve times its weight of water, allowing the mixture to stand for half an hour, and collecting and weighing the sand which will be found at the bottom of the vessel employed. If there be bran present it will be found lying on the sand, and its structure is sufficiently distinct to admit of its detection by a mere glance. There are a great variety of linseed-cakes in the market, of which the home-made article is the best. On the Continent the oil-seeds are subjected to the action of heat in order to obtain from them a greater yield of oil. Their cakes, therefore, contain less oil, and their flesh-forming principles are less soluble, in comparison with British linseed-cake. Next to our home-made oil-cakes, the American is the best. Indeed, I have met with some American cakes which were equal to the best English. _Rape Cake._--The use of rape-cake was limited almost completely to the fertilising of the soil until the late Mr. Pusey, in a paper published in the tenth volume of the _Journal of the Royal Agricultural Society of England_, advocated its employment as a substitute for the more costly linseed-cake. The recommendation of this distinguished agriculturist has not been disregarded; and since his time the use of this cake as a feeding stuff has been steadily on the increase, and at the present time its annual consumption is not far short of 50,000 tons.