EARTHS experiments were made by Hassenfratz Saussure, and others, with the same und vourable result. Duhamel found that an oak, which he had raised from an acorn in common water, made less and less progress every year. The florist is well aware that bulbous roots, such as those of hyacinths, tulipe, &c. which are made to grow in water, unless they are planted in the earth every other year, at first refuse to Bower, and finally they cease even to vegetate. Moreover, it has been unanswerably shown by many very accurate experiments at the repetition of which I have personally assisted, that the quantity of nourishment or solid matters absorbed by the roots of plants is always in proportion to the impurity of the water with which they are nourished; thus some common garden beans were made to vegetate under three different circumstances; the first were grown in distilled water, the second were placed in sand and watered with rain water, the third were sown in garden mould. The plants thus produced, when accurately analysed, were found to yield the following proportion of ashes Parts. • 7.5 - 12-0 1. Those fed by distilled water 3-9 2. Those fed by rain water 3. Those grown in the soil The mode in which the earths are absorbed by the roots of the plant is, it is almost certain, by means of their solution in water, for both carbonate of lime and silica are, in small proportions, soluble in water; they exist together in many springs; and they were both found in the water of the Clyde by Dr. Thomson, in that of the Thames by Dr. Bostock, and in the springs of Upsala, celebrated for their purity, by Bergman. Alumina, as far as we know, is not soluble in water, but then it exists in very small proportions in plants; and the soluble salts of which it is the base may serve to yield this earth to vegetables: the earth itself is soluble in ammonia. The way in which soils are gradually formed by the action of the atmosphere upon the hard primitive rocks has been well explained by Davy, and is a natural process which cannot but be interesting to the farmer. I merely slightly alter his words in the following account of this important natural phenomenon. It is not difficult to comprehend the manner in which this change is effected, and rocks converted into soils, by referring to the instance of soft granite or porcelain granite. This substance is composed of three ingredients, quartz, felspar, and mica. The quartz is almost pure silicious earth in a crystalline form. felspar and mica are very compound sub The ; and Ikewise the mic bush fr he mus rapolly. The fuser, with E. #I V the cement of the stone, items 1 ime cir the mica party decomposed, mis vri it as sand and the memorset pur appears as grave, or sad or diferent t grees of freness. As soon as the muless layer of earth is thus formed in the surface of a rock, the seeds of Sciens, noses, mé other imperfect repetatues, vira are mastantly Boating the mosphere, and which have made it their resting pure, bern to vegetale: their death. dempesta m decay afford a certain quantity of terene matter, which mixes with the earthy naterials of the rock. In this improved soil more perfect plants are capable of saONINGINE these in their turn absorb nourishment from water and from the atmosphere, and as these, too, decay, afford more new materials to those already provided; and the decomposition of the rock still contin pes. length, by such slow and almost impercentible processes, a soil is formed in which even forest trees can fix their roots, and which is fitted to reward the labours of the cultivator. Where successive generations of vezetables have grown upon a soil, unless they have been carried off by man or consumed by animals, the vegetable matter increases to such an extent that the soil approaches to peat in its nature. Poor and hungry soils are commonly produced by the decomposition of the granite and sandstone rocks: such soils usually remain for ages with only a thin covering of vegetation. The soils produced by the same gradual means on the limestones, chalks, and basalts, are often clothed by nature with the perennial grasses; and afford, when ploughed up, a rich bed of vegetation for every species of cultivated crop. The quantity of moisture which a soil, or the earths of which it is chiefly composed, contain, influences to a very material extent its fertility. This not only differs in different seasons, but this power varies very considerably indeed in soils, according to their chemical composition. This was experimentally decided by Professor Schubler, of the University of Tubingen, in his "Agronomy, or Principles of Agricultural Chemistry," for a translation of which the English farmer is indebted to Mr. Hudson, the present excellent Secretary to the Royal Agricultural Society of England,—a translation of which I have largely availed myself in this paper. (Journ. of Roy. Ag. Soc. vol. i. p. 177.) M. Schubler found that a cubic foot of different soils, when thoroughly saturated with water and when completely dried, weighed as follows: Gypsum powder 136 Very light Turf soil 132 Dry. Wet. Slaty Marl 131 Arable soil 131 Stiff Clay or brick lbs. lbs. 2.722 113.6 141.3 2.653 111.3 136.1 2.331 91.9 127.6 2.601 97.8 129.7 2.581 88.5 124.1 2.560 80.3 119.6 2.553 75.2 115.8 2.440 47.9 102.1 2.468 53.7 103.5 2.332 68.7 102.7 2.401 84.5 119-1 2.631 112.0 140.3 The result of these trials will be useful to the farmer in explaining to him the reason why, on account of their requiring more or less moisture, certain crops flourish best on particular soils; and even in the carriage of the earths he will perceive that their weight in the wet or dry state is much greater than some persons suppose. The next important inquiry instituted by the same excellent chemist, was the relative degree of tenacity with which different soils retain the moisture when exposed under similar circumstances to the action of the atmosphere, and he found that they parted with their moisture according to the following rate : Black Turf Soil not so light White fine Clay Grey fine Clay The amount of the relative contraction of different soils, when they are deprived of their moisture, is another equally important question to the farmer to be ascertained. Many of them," says M. Schubler, "become contracted into a narrower space in drying, and in consequence of this circumstance cracks and fissures frequently occur in land, and have an injurious effect on the vegetation, as the finer roots, which often ramify horizontally, and not unfrequently supply to the plants the greater part of their means of nourishment, are, by such contractions, either laid bare of soil or torn asunder. In order to subject soils to comparative experiments on this point, the following plan may be adopted. We either form of the earths, in their wet state, large cubic pieces of equal size, being at least ten-twelfths of an inch in height, breadth, and length, or we let such earths be fitted and dried one after another in an accurately worked cubic inch; after some time, when the weight of these cubes of earth ceases to change by further drying, we measure the EARTHS. of any. - | A still more important property of soils, heir attraction for the aqueous vapour of the atmosphere, is next to be considered – property the importance of which to the ltivator, Sir H. Davy long since saw in its rue light, and his observations cannot be too ften quoted, since they well illustrate and force, amongst other things, the truth of he great Tullian system of agriculture,- of The advantages of finely dividing the soil, of he subsoil plough, and of the horse-hoe usbandry. "The power of the soil to absorb water by cohesive attraction," said this great hemist, "depends in a great measure on the tate of division of its parts; the more diided they are, the greater is their absorbent power. The different constituent parts of soils likewise appear to act, even by cohesive attraction, with different degrees of energy: thus vegetable substances seem to be more absorbent than animal substances, animal substances more so than compounds of alumina and silica, and compounds of alumina and silica more absorbent than carbonates of lime and magnesia; these differences may, however, possibly depend upon the differences in their state of division, and upon the surface exposed. The power of soils to absorb water from air is much connected with fertility; when this power is great, the plant is supplied with moisture in dry seasons; and the effect of evaporation in the day is counteracted by the absorption of aqueous vapour from the atmosphere by the exterior parts of the soil during the night. The stiff clays, approaching to pipe-clay in their nature, which take up the greatest quantity of water when it is poured upon them in a fluid form, are not the soils which absorb most moisture from the atmosphere in dry weather; they cake, and present only a small surface to the air, and the vegetation on them is generally burnt up almost as readily as on sands. The soils that are most efficient in supplying the plant with water by atmospheric absorption are those in which there is a due mixture of sand, finely divided clay and carbonate of lime, with some animal or vegetable matter; and which are so loose and light as to be freely permeable to the atmosphere. With respect to this quality, carbonate of lime and animal and vegetable matter are of great use in soils; they give absorbent power to the soil without giving it tenacity: sand, which also destroys tenacity, on the contrary, gives little absorbent power. I have compared the absorbent powers of many soils with respect to atmospheric moisture, and I have always found it greatest in the most fertile soils; so that it affords one method of judging of the productiveness of land. 1000 parts of a celebrated soil from Ormiston in East Lothian, which contained more than half its weight of finely divided matter, of which eleven parts were carbonate of lime, and nine parts vegetable matter, when dried at 212° gained in an hour, by exposure to air saturated with moisture at a temperature of 62°, 18 parts; 1000 parts of a very fertile soil from the banks of the river Parret, in Somersetshire, under the same circumstances, gained 16 grains; 1000 parts of a soil from Mersea, in Essex, worth forty-five shillings an acre, gained 13 grains; 1000 grains of a fine sand from Essex, worth twenty-three shillings an acre, gained 11 grains; 1000 of a coarse sand, worth fifteen shillings an acre, gained only 8 grains; 1000 of the soil of Bagshot Heath gained only 3 grains." In my own experiments upon the absorbent powers of various earths, I extended the examination to various organic and saline fertilizers. The result of these may be seen in the following table : Another property possessed by all cultivated soils, that of absorbing the gases of the atmosphere and of putrefaction, is a power equally worthy of the consideration of the farmer. It was long since shown, in some experimental reseaches of Mr. Hill, that when oxygen gas is supplied to the roots of plants, their growth and vigour are very considerably increased. Some years since, also, Alexander Von Humboldt announced that the earths possess the property of absorbing this gas from the atmosphere (Gilbert's An. of Phil. vol. i. p. 512.; and although the fact was doubted at the time, yet later researches have shown that moist earth has the property assigned to it by Humboldt, and the amount absorbed by various earths has since been ascertained by, Silicious Sand Calcareous Sand Gypsum powder Sandy Clay Loamy Clay Stiff Clay or brick earth Gray pure Clay Fine Lime Magnesia Garden Mould Absorbed in the dry state. In the wet state ab sorbed in 30 dim by 1000 grains of Earth from 25 bic inches of Atme spheric Ar, ce taining 1 per cent of Oxygen. grains. 010 0:35 0.17 F 0:59 0-70 0-86 0-97 0-69 1-08 1.10 1-03 0.70 This attractive power of the earths and of the plants for the aqueous vapour and lat oxygen gas of the atmosphere are, as I have on more than one occasion contended, tw of the most important facts to be kept in mind by the farmer, with regard to the deepening and pulverisation of his sous The power of absorbing moisture is a power which all plants possess in a certain me sure, but some in such a perfect degree. to depend entirely upon it for all the mos ture they need. The aloe, the agave, a many of the native plants of the East, nearly support themselves in the same way; lichens and some of the mosses of t country almost do the same. The quart of water consumed by plants, when in a state of healthy vegetation, is in fact great that, if it was not for the gentle steady supply thus imperceptibly furnished to the soil by the atmosphere, vegetation wou speedily cease, or only be supported by in cessant rains. Thus. Dr. Hales ascertai that a cabbage transmits into the atm phere, by insensible vapour, about hal height of water daily; and that a sunflow three feet in height, transpired in the sa period nearly two pounds' weight. (Te Stat. vol. i. pp. 5-15.) Dr. Woodward found that a sprig of mint, weighing grains, in seventy-seven days emitted 24 grains of water. A sprig of spear weighing 27 grains emitted in the same t 2558 grains; a sprig of common nightshade weighing 49 grains evolved 3708 grains. 4 a Lathyrus of 98 grains emitted 2501 gra (Phil. Trans. 1699, p. 193.) "The po of soils to absorb moisture," Davy "ought to be much greater in warm or countries than in cold or moist ones, the quantity of clay or vegetable or an matter greater. Soils, also, on declivian says EARTHS. ought to be more absorbent than in plains, or in the bottom of valleys. Their productiveness, likewise, is influenced by the nature of the subsoil, or the stratum on which they rest. When soils are immediately situated upon a bed of rock or stone, they are much sooner rendered dry by evaporation than where the subsoil is of clay or marl; and a prime cause of the great fertility of land in the moist climate of Ireland is the proximity of the rocky strata to the soil. A clayey subsoil will sometimes be of material advantage to a sandy soil; and, in this case, it will retain moisture in such a manner as to be capable of supplying that lost by the earth above, in consequence of evaporation or the consumption of plants." (Dary's Lectures, p. 186.) rendered permeable, the greater will be the absorption by them of both oxygen and watery vapour from the surrounding atmosphere. It is perhaps needless to prove that the roots of commonly cultivated plants will penetrate, under favourable circumstances, much greater depths into the soil in search of moisture than they can, from the resistance of the case-hardened subsoil, commonly attain. Thus, the roots of the wheat plant, in loose deep soils, have been found to descend to a depth of two or three feet, or even more: and it is evident that if plants are principally sustained in dry weather by the atmospheric aqueous vapour absorbed by the soil, that then that supply of water must be necessarily increased, by enabling the atmospheric vapour and gases, as well as the roots of plants, to attain to a greater depth; for the earth, &c. of the interior of a well pulverised soil, be it remembered, continues steadily to absorb this essential food of vegetables, even when the surface of the earth is drying in the sun. By facilitating the admission of air to the soil another advantage is obtained, that of increasing its temperature. The earths are naturally bad conductors of heat, especially downwards: thus, it is a well-known fact, that at the siege of Gibraltar, the red hot balls employed by the garrison were readily carried from the furnaces to the batteries in wooden barrows, whose bottoms were merely covered with earth. Davy proved the superior rapidity with which a loose black soil was heated, compared with a chalky soil, by placing equal portions of each in the sunshine; the first was heated in an hour from 65° to 88°, while the chalk was only heated 69°. This trial, however, must not be regarded as absolutely conclusive, since the surface of the black soils naturally increases more rapidly in tempera ture when exposed to the direct rays of the sun than those of a lighter colour. A free access of the air to the soil also adds to the fertility, by promoting the decomposition đ the excretory matters of plants and other organic substances of the soil. It has been shown by the experiments of M. Saussure, with some sprigs of peppermint, that when supported by pure water nly, and allowed to vegetate for some ime in the light, they nearly doubled the ortion of carbon which they originally ontained. (Recherches sur la Veg. 51.) This they could have procured only from he atmosphere; and, under these circumtances, there is now little doubt of the orrectness of the conclusion of M. Berbollet, that plants, by means of their roots nd leaves, have the power of decomposing he water as well as the carbonic acid of he atmosphere, and furnishing, with these lements, new combinations. How essenial a free access of the atmosphere is to the bots of plants was long since shown by Saussure, who found that oxygen gas absorbed by the roots of plants as well 8 by their leaves, and that it is at the oots united with carbon, and transmitted the leaves to be decomposed. Even the ranches absorb oxygen; in its absence lowers will not even expand. (Thomson's Them. vol. iv. p. 353.) It has been proved hat their vegetation is greatly increased by ourishing them with water impregnated ith oxygen gas; hence, too, the superiority f rain water. Some remarkable experinents were made by Mr. Hill, demonstraive of the great benefits plants derive from xygen gas being applied to their roots: In the truth of these conclusions and la yacinths, melons, Indian corn, &c. were borious experimental reseaches of the cher be subjects of the experiments. The first mist, does not the practical testimony of were greatly improved in beauty, the second the ablest cultivators of all ages and in all n flavour, the last in size, and all in vigour. countries concur? Thus, in enforcing the This, too, is another use of increasing the advantages of rendering the soil more com noisture of the soil, by deep and complete pletely permeable by the atmosphere, nearly ploughings, for M. Humboldt and M. two thousand years since, Cato asked the Schubler have clearly shown that a dry soil Italian farmers, "What is good tillage?" quite incapable of absorbing oxygen gas. To plough. What is the second?" To Thus, it must be evident to the most list-plough. The third is to manure, less observer, that the more deeply and however, mistook the cause of the bendit, finely a soil is pulverised, and its earths for he says, " He who stirs his olive groundi Cato |