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As this substance is beginning to be extensively used by our farmers, and as there are many indifferent kinds of it, and perhaps considerable adulteration practiced, it will no doubt be a benefit to farmers to be able to judge correctly of its quality. Common guano is a mixture of ammenia- cal salts and earthy phosphates, and is composed of the excresences of sea fowl, deposited on islands in the sea, in latitudes where no rains fall. It is brought to the United States and Europe from two different parts of the world, viz., Africa and Peru; the former kind contains a larger amount of phosphates but less ammonia than the latter, and is therefore inferior. Guano contains water, ammonia, ulmic, uric, and humic acids, which are classified as volatile and organic matter, separable at a low red heat; also alkaline salts, such as sulphate of soda, chloride of sodium, and alkaline phosphates which are separable by boiling water from the aforesaid ash ; also earthy salts, consisting of the carbonates and phosphates separable by hydrochloric acid from the residue aforesaid ; also sand which is insoluble. To analyse guano :—1st, calcine 100 grains in a capsule at a low red heat, until all black particles are burnt away and a white ash is left. Good guano should lose about from 60 to 70 per cent, of volatile matter. 2nd, digest the above ash salts, filter them, then dry the residue and weigh it. Good guano should lose from 4 to 6 per cent. ofthese alkaline salts. (The phosphoric acid can be separated from this solution by adding sulphate of magnesia and ammonia, which precipitate it as ammoniac phosphate of magnesia.) 3rd, The residue of the above is then digested in hot hydrochloric acid, then filtered and well washed; then weighed, the loss is carbonate and phosphate ot lime and magnesia, which are precipitated by ammonia, this, on being dried and submitted to heat should amount to 15 or 20 per cent. of the whole guano. 4th The residue is sand and should never exceed four or five per cent. in good guano. One sign of good guano is, that from fifty to seventy per eent. should dissolve in a hob solution of caustic potash with a strong smell of ammonia; trom thirty to torty-seven per cent. of good guano is soluble in water. It would be well if every planter and farmer had a small laboratory for experiments, always taking care to be as economical of time for out-door business as possible. We ad vise our young farmers to cultivate a taste for chemistry and experiment; it is a science founded altogether on experiment. We can tell why two and two makes four in mathematics, but we cannot tell why oxygen and hydrogen combine in certain definite proportions and no others, to form water ; we know that it is so by experiment, and the fact is an important one. There are many facts yet to be discovered, and agricultural chemistry offers a wide field for investigation.
