straw, which, after it has served as litter, would, beyond this, be a comparatively useless refuse of our grain crops, phosphoric acid is found to be a very active agent; while of the nitrogen stored up in the growth of the root crop, a much larger proportion than of the carbon remains in the excrement of the animals, and serves in turn for the growth of succeeding cereal grain; hence there is a mutual reliance between these two important crops of rotation. There is another point in connexion with the great demand made by the wheat plant upon nitrogen supplied to the soil. Among from 200 to 300 experiments with ammoniacal manures, the increased amount of nitrogen provided in the manure has not been recovered in a single instance. This fact is perfectly consistent with the amounts of produce found, by general experience, to be obtained by Peruvian guano and other nitrogenous manures. The results of experiments made by the authors, and published in the Journal of the Horticultural Society (January 1850), show that while, for a given quantity of water passed through a plant during its growth, the amount of nonnitrogenous substances fixed in it is, within somewhat narrow limits, identical; that of the nitrogenous proximates fixed is, on the other hand, about twice as great in the Leguminosa (beans, peas, &c.), as in the Graminacea (grasses). This agrees perfectly with the results of their field experiments with wheat and beans respectively, which show that under the same circumstances of growth, as to manure, &c., and in the same season, the acreage yield of nitrogen is twice or thrice as great in beans as in wheat. Yet it cannot be supposed that the larger amount of nitrogen harvested in the leguminous crop would proportionately exhaust the soil of this element; for common practice teaches that, other things being equal, wheat which is especially dependent on the supply of nitrogen in the soil, would give a larger produce after a bean than after a wheat crop. Hence it would appear that the leguminous plants possess a greater power than the graminaceous of obtaining nitrogen from the atmosphere rather than from the soil; or it may be supposed that the expenditure of it during the growth of the plant is greater in one case than in the other. The experiments of M. Boussingault support the view that legu minous plants possess a superior power of obtaining nitrogen from the atmosphere; and Leguminosa, both beans and other seed-crops and clover, appear to profit most by a mineral and especially alkaline manure. Fallow crops generally indeed, or those which alternate with grain, appear to derive essential service from direct mineral manures, as enabling them to accumulate nitrogen from the atmosphere. This fact would be in agreement with Liebig's theory. The dependence of one plant on another for luxuriant growth is also beautifully illustrated by the "fairy rings," where the grass grows so richly upon the decayed fungi which have fixed a large quantity of nitrogen from the atmosphere. Again, judging from the composition of the ash of the turnip, which shows, both in the leaf and the root, a proportion of alkalies to phosphoric acid of from 4 or 5 to 1, we might be led to suppose that the former rather than the latter were usually and especially the more appropriate manure for turnips. But common practice has definitely decided in favour of phosphoric acid rather than alkalies, as the special manure to be provided for the turnip beyond the manures found on the farm itself; and the authors have no hesitation in saying, in opposition to Liebig, that however small the quantity of phosphates contained in the turnip, the successful cultivation of it depends more upon a large supply of phosphoric acid in the manure than that of any other crop. Messrs. Lawes and Gilbert believe the extraordinary effect of superphosphate of lime on root crops to be attributable to a specific action upon the assimilative processes of the plants, and this opinion is favoured by the fact, that in cases where the superphosphate of lime is at once neutralized by alkalies supplied artificially, the efficacy of the manure seems to be thereby reduced; and from this again it is concluded that the effect of the phosphoric acid, as such, cannot be due merely to the liberation within the soil of its alkalies, since then it might be supposed that the artificial supply of these would have been attended with at least some increase of produce. But this was not the case, notwithstanding that by means of superphosphate of lime alone there has been taken from the land more of the alkalies in which the ash of the turnip so peculiarly abounds, than would be lost from it in a century under the ordinary course of rotation and. home-manuring. Collateral experiments also clearly prove the importance of a liberal supply of organic substance rich in carbon-which always contains a considerable quantity of nitrogen also-if we would, in practical agriculture, increase the yield much beyond the amount which can be obtained by mineral manures alone; and these conditions fulfilled, the direct supply of nitrogen is by no means so generally essential. ON THE USE OF SALT AS A MANURE. MR. A. B. NORTHCOTE has recently published in the Philosophical Magazine (for Sept. 1855) some interesting experiments on the function of salt in agriculture. He sums up his conclusions in the following terms : "The results, then, at which we must arrive are, that agricultural salt is a most energetic absorbent of ammonia, both in virtue of its chloride of sodium and of its soluble lime-salt, and that the proportion of the latter especially most powerfully affects its action;-but that at the same time its agency does not seem to be altogether a permanent one: it will collect the ammonia, but it is questionable whether it can retain it for any great length of time, because in the very decompositions which happen in order to render the ammonia more stable, salts are formed which have a direct tendency to liberate ammonia from its more fixed combinations. It may, however, retain it quite long enough for agricultural purposes: if the young plants are there ready to receive it, its state of gradual liberation may be for them the most advantageous possible; and to this conclusion all experiments on the large scale appear most obviously to tend. It is described as an excellent check to the too forcing power of guano; and from M. Barral's experiment we see that it either prevents the too rapid eremacausis of the latter, or stores up the ammonia as it is formed. As a manure for growing crops, all experience and all theoretical considerations therefore show it to be most valuable; but when employed to mix with manure heaps which have to stand for considerable periods of time, theory would pronounce, as practice has in many cases done, that its power of retaining ammonia under those circumstances is at the best doubtful." THE NEW SYSTEM OF IRRIGATING LAND BY MEANS OF SUBTERRANEAN IRON PIPES WITH HOSE AND JET. I AM SO frequently questioned as to the cost and success of this operation, that I purpose, as briefly as possible, giving the necessary information. Supposing the farm to be of 200 acres, pipes of 3 inches diameter would be sufficiently large : Cost per acre. 15 yards of 3-inch iron pipe, weight 5 cwt. at A liquid manure tank of 4 inch brick-work, 200 yards of gutta percha 2-inch tubing, at £ s. d. 2 1 3 0 15 0 0 10 0 600 0 10 0 So that about £5 per acre will be the cost of the whole operation; this is considerably higher than the estimates quoted by the General Board of Health, page 136 (whose paper on this subject every body should read), and much higher than my own expense; because when I carried out this operation in March 1852, the price of iron pipes was only £4 58. per ton, labour, materials, &c. in proportion. I think I have somewhat over-estimated the cost, but there are always a number of incidental expenses which tend to enlarge the estimate. Assuming 7 per cent. on the sunk capital to be a sufficient charge, your fixed charge on every acre of the farm will be 7s. 6d., and your working expenses will be as follow on the land actually irrigated : 6-horse power, or 7 cwt. of coals per diem Man and youth to work jet, 2s. 6d., 1s. 6d. S. d. 8 2 4 1 15 060016 or 15s. 6d. per diem working expenses. With this power you will put on 5000 gallons per hour, or 50,000 gallons in ten working hours; allowing two hours on each acre, or 10,000 gallons per acre, the cost for each dressing per acre will be 3s. 1d. Supposing the grass or other crop requires four dressings per year, the cost would be 12s. 4d. per acre on the land actually irrigated. It is now three years and a half since I first began irrigating, and I have no hesitation in saying that the operation is a profitable one. By this process you intimately admix your manure with every granule of the soil and subsoil to the depth of the drains, which I have often seen discharging the liquid at 4 and 5 feet deep. A cross cut in our ordinary soils exhibits 5 inches of friable and well-looking soil, whilst all below shows undisturbed poverty. Irrigation remedies this and fertilizes where the ploughiron never enters. In the practical working of the operation, a hundred difficulties presented themselves; these have all been overcome, (as with steam, gas and other new inventions); and now our men pursue their avocation without let or hindrance. I have written largely on this subject in the Agricultural Gazette and under the head 'Sewage' in Blackie's Cyclopædia of Agriculture. The main difficulties that have been overcome were-the avoidance of concussion by ample air-vessels, the intermixture and suspension of the solid manure by constant agitation produced by an impulsion of air from an air-pump. The substitution of a gutta percha suction pipe with corrugated joints instead of iron pipes. The use of a large suction gutta percha bulb with many holes, by which the manure is gradually and slowly drawn in, thereby avoiding the choking, which was caused by a violent rush through limited openings. Painting the gutta percha tubing white to prevent its melting in summer by the heat of the sun. Inserting corrugated joints, at intervals of 18 feet, to enable the gutta percha tubing to curve without "knuckling." Improving the draught and setting of my steam-boiler, by a strict adherence to the rules laid down in Mr. W. Wil |