_The adulteration of guano_ is carried to a great extent in England, and probably will be in this country. The principal adulterations are made by the addition of loam, marl, sand, plaster, old lime, ashes, chalk, salt, moisture, and by mixture with other guano of a cheaper quality. The farmer need not depend upon the assertion, "this is a genuine article--here is the inspector's certificate." We would not give a straw for a corn basket full of certificates of analysis. The buyer must analyse for himself. Mr. Nesbit, analytical chemist, London, has just published a pamphlet from which we have condensed some very plain, short, simple rules for testing the quality of guano. As the adulterating substances are generally heavier than the guano, they may be detected by a comparison of weight and measure. To do this, get a small glass tube closed at one end, and weigh accurately an ounce of pure guano, put it in the tube and carefully mark the hight it fills--try several samples--if there is any difference, mark it. Now weigh an ounce from a sample adulterated with one fourth its bulk of any or all the preceding list of articles used for that purpose, and you will find the difference of bulk between that and the genuine, very perceptible. _Test by Burning._--Guano burnt to ashes at a red heat will leave an ash of a pearly white appearance, not varying in weight from 30 to 35 per cent. of the quantity burnt. If it is adulterated with marl, sand, clay, &c., the ash will be about 60 or 65 per cent, of the weight tested, and be colored with the iron always present in the adulterating substances, and which is never found in pure guano. This test, to be accurate, must be done with a nice pair of scales and a platinum cup, which may be heated over a spirit lamp. Ten grains of the guano are placed in the platinum cup, which is held by the tongs in the flame of the spirit lamp for several minutes, until the greater part of the organic matter is burnt away. It is allowed to cool for a short time, and a few drops of a strong solution of nitrate of ammonia added, to assist in consuming the carbon in the residue. The cup is again heated, (taking care to prevent its boiling over, or losing any of the ash,) until the moisture is quite evaporated. A full red heat must then be given it, when, if the guano be pure, the ash will be pearly white, and will not exceed 3-1/2 grains in weight. If adulterated with sand, marl, &c., the ash will always be colored, and will weigh more than 3-1/2 grains. Even the simple burning of a few grains of guano, on a red hot shovel, will often indicate by the color whether a fraud has been committed; but we cannot particularly recommend this method, as the iron of the shovel itself will sometimes give a tinge to the ash. This might be obviated by burning the sample on a common earthen plate.