Chemical. Field Lectures for Agriculturists. By Dr. Julius Adolphus Stocehaedt, Professor in the Royal Academy at Tharand. Translated from the German. Edited, with Notes, by James E. Teschemacher. Cambridge: John Bartlett. 1853.

There is so much that is technical, speculative, and visionary in most of the writings on the Chemistry of Agriclture that the title of "Chemical Lectures" will be somewhat uninviting to plain, practical cultivators; but we can assure them that this is not a book of speculation. On the contrary, it is as plain and intelligible as any book can possibly be, and treats the all-important questions concerning the composition, relative value, and mode of applying the various substances used as fertilizers, in such a way as every farmer and gardener can perfectly well understand and appreciate.

No sensible man, who cultivates the soil, will say, "I do not need such a book, I know all about manures." If we heard any one say so, we should fear that he was hopelessly ignorant; for however old, or wise, or experienced we are, we have much to learn; and in regard to the best and most economical manners and modes of applying manure in such a way as will best promote the growth of the various field and garden products, we have nearly everything to learn. "We have looked through but two or three chapters of this book, yet we have gleaned a few very useful hints that we shall soon carry into practice.

The following extract in relation to guano conveys an idea of the simple and practical character of the work:

"For a thorough manuring, the average reckoning is 4 cwt of guano to the Saxon acre, or a full 2 owl to the Prussian Morgen.* Yet this amount, according to climate and soil, more particularly in mountainous districts, is frequently exceeded; while, on the contrary, a less .quantity may be sufficient where climate and soil are peouliarly favorable.

"On the mode of application + the following remarks must be made. Firsts the guano must be prepared. This preparation is very simple, and consists in reducing it to a homogeneous, pulverulent mass, and mixing it with earth. The first is effected upon a barn floor, by sifting and threshing. The finer portion is first rifted off; then the remaining lumps and fragments of larger site are threshed, and again sifted, until they are likewise converted into powder. The last portions of the residue are often so yielding and viscid, that they flatten upon being struck with the flail, and will not pass through the sieve. In this event they may be either beaten together with a brick or stone, by which means they are easily reduced to powder or they may be added to the compost heaps which are absent on no good farm. The sifted guano should now be mingled with from twice to three times the same quantity of earth, or with a mixture of earth and aches, and the whole shovelled together, until a thorough and entirely uniform mixture is effected.

The earth must possess the ordinary state of moisture, in which it easily absorbs the guano without forming into balls or lumpa It is a good plan to make the mixture at least from four to six days before it is scattered over the soil; and still better to undertake its preparation at a convenient time, before work presses on the farm, for it very often happens that farming labor is crowded into sowing time, and the mixture of the guano with earth is then executed hastily and unsvs-tematically, or perhaps not at ail, the consequences of which are very injurious. I£ however, the mixture is already at hand, these prejudicial consequences are avoided. The scattering in the field is best managed in the same way as that in which lime is usually put upon the land, or by spread-ing from a seed-bag. It is well to strew it upon the last plowing some two or three days before introducing the seed, and then lightly harrow; on a light soil, to roll, and after this to harrow in the seed. Moist weather, during its application to the soil, (especially in spring or summer sowing,) exerts a very beneficial influence upon the action of guano.

" * Literally, as much land as a man can plow in a morning; - about an English acre.

" + It would not be proper to pass over this mode of preparation without some further notice.

"If a glass rod moistened with muriatic acid be held an inch distant from the surface of a saueerfnl of Perarlan guano Just taken from the bag in which it is imported, a white cloud will be immediately perceived. This is formed by the union of the ammonia rising up and evaporating from the guano with the fames of the muriatic add, rendering it manifest that ammonia escapes from guano very readily at the usual temperature of the atmosphere, - of course more abundantly in hot than in cold weather. Hence it is evident that the exposure during the pounding and frequent sifting here recommended must be very injurious to the guano, and cause the loss of much of its most valuable ingredient.

" It is much preferable to start the bags on the barn-yard floor, and, after spreading out the guano au inch thick-, quickly to cover it with powdered charcoal or fine burnt bone-black, the refuse of sugar refineries, or with dry gypsum, or with clay which has been rendered friable by exposure to frost and then broken up and dried moderately, or with all these substances together; thus spread layer upon layer alternately, and finish by eovermg up with the empty bags, and putting over these a final coating of any of these absorbing substances. In this way the ammonia will suffer very little diminution, and the mixture will be sufficiently incorporated when taken on the land, and plowed or drilled in, without the labor and loss attendant on turning over. The small lumps may be left in without prejudice; the few large ones may be easily separated by hand, and broken afterwarda - J. E. T.

"The addition of earth is beneficial in a great variety of ways. Pure and good guano is so rich in ammoniacal salts, as easily to corrode the tender roots of plants, more particularly in dry weather; by mixing it with earth, it is so enveloped and weakened that this injurious effect is no longer to be feared. In this way, moreover, just as in the covering over muck heaps with earth, the possible escape of aeriform manuring elements from the guano is cut off, since the porous earth has the property of absorbing and firmly holding these substances. Finally, by the addition of earth a more uniform distribution of the mass upon the land is rendered practicable, and the flying off of dust during dispersion prevented; - an inconvenience that otherwise is likely to occur, and may occasion inflammation of the eyes and other annoyances to the laborer.

" With potatoes, green crops, roots, do., a handful of the mingled earth and guano may be given to every plant in dibbling or planting. A little more than a quarter of an ounce of bird-manure, costing the fourth part of a farthing, serves in this way as an exclusive manuring for a plant With other manures a third or fourth part of this quantity, whose value will not therefore exceed the twelfth or sixteenth of"a farthing, causes a very marked increase of growth. Equally certain results are obtained if the mixture of earth and guano is scattered with as great uniformity as possible in the ridges in which potato sets are laid, or if, in case the guano should not at that moment be at hand, it is strewed over the surface of the field after the young plants have already sprouted up but may still be passed over with the harrow; - a mode of treatment that is confessedly of great advantage when the potatoes have attained the height of some four inches above the ground, and must soon be earthed up. Garden produce may be treated in either of these methods; for such plants, however, as also for grass and meadow land, watering with a solution of guano may be strongly recommended.

For this purpose, one part of bird-manure should be treated with at least from 80 to 100 parts of water; since, if too strong, the solution of guano exerts a corrosive action upon young and tender plants.

" For top-dressing, which should be employed as circumstances may make advisable, in the autumn or early spring, guano is in like manner most judiciously employed when mixed with earth".

The work is for sale by D. M. Dewey, of Rochester, who has been kind enough to place it before us.