These results show to what extent gypsum is favorable to the production of sainfoin. The cro, from the unplastered breadth being taken as 100, that upon the plastered breadth is 231; it is more than doubled. The influence of gypsum was also found by Smith to extend to grain; assuming the grain crops on the ungypsed land at 100, those on the gypsed soil were 192; they were nearly doubled. On comparing the weight of the herbaceous portion of the sain foin to that of the seed produced, widely different relations are apparent. These Mr. Smith attributed to the different depths of the vegetable soil in different parts of the field. In the first experiment, where the relative proportion of seed is highest, the arable soil was three feet in thickness; the other crops were taken from parts where the depth of vegetable mould was considerably less. Thus the gypsed soil produced at the rate per acre : cwts. qrs. lbs. 0 22 the depth of soil being 3 feet. 1 1 15 3 15 แ 18 inches. 3 inches. In the first experiment of 5 In the second experiment of 3 In the third experiment of With this interesting fact before him, Mr. Smith imagined that soils of little depth wanted some principle essential to fructification, which gypsum, in spite of the unquestionable assistance it gives, is yet incompetent to supply. This principle is in all probability organic matter, which is naturally more abundant in the layer of true vegetable mould which is deepest. Mr. Smith's observations on white clover were quite as decisive in favor of gypsum as those on sainfoin, and are confirmatory of the conclusions of the generality of farmers on the subject. The gypsum in connection with this crop was applied in the dose of 6 bushels per acre, on the 22d of May, a date at which the clover looked pale, and seemed to want sap. A fortnight afterwards, the effects of the gypsum were obvious; although no rain had fallen in the in terval, the clover had become vigorous, and soon formed a covering thick enough to protect the ground from the scorching rays of the sun, which burned up all the parts which had not been gypsed. COMPARATIVE GROWTHS OF WHITE CLOVER, GYPSED AND UNGYPSED, BY MR. SMITH. The mean of these two experiments shows that the crop of white clover on the ungypsed land being 100, that on the gypsed is 225— twice and a quarter more. The experiments of M. de Villèle may be viewed as supplemen tary or complementary to those of Mr. Smith. They were performed in the south of France, in accordance with the routine that is generally followed, viz: clover-hay, or sainfoin, previous to grain, upon soils of considerably different nature, and with doses of gypsum that varied from 8 to 3 on the same extent of surface. conclusions or crops are stated in the following table : His cwt.qr.cwt.qr.lbs.cwt.qr.lbs. cwt.qr.lbs. s. d. 8. d. s. d. Light, dry, exposed to the south, 6 to 9 inches deep, and on chalk.J Stony clayey, moist, about 16 inch. deep on a stiff clay. 1 Sainfoin 6 3 28 2 6 18 0 1 10 2 15 17 7 6 9 10 10 2 Sainfoin 2 2 Clover 493 17 18 1 23 13 0 11 31813 314 1 4 0 40 19 20 20 1 23 10 2 2 The unquestionable fact of a mineral salt stimulating the growth of certain plants in so remarkable a manner as to double and even to triple the usual quantities grown per acre, naturally aroused the curiosity of mankind to inquire into and endeavor to discover the cause Explanations in abundance have been proposed; but so little satisfactory in general, that I do not think myself bound to mention them all. I shall limit myself, indeed, to two; one proposed by Davy some time ago, and one advocated by Liebig very lately. Davy assumes that the plants of artificial meadows simply absorb sulphate of lime. He assures us that he had found a large proportion of this salt in the ashes of vegetables grown in soil which had been treated with turf ashes abounding in the substance. He believed that the gypsum entered particularly into the constitution of the woody fibre. And it is not uninteresting to observe, that the plants which gypsum certainly favors in the highest degree, are of very rapid growth; and that in all probability they would find it difficult to obtain the whole of the sulphate of lime they require from ordinary or ungypsed soils within the period of their growth. Let it not be forgotten, however, that if it be true that saline substances are indispensable to the organization of plants, it is also true that these substances can only be absorbed within certain limits; a salt the best calculated by its nature to aid vegetation, would become injurious by its excessive proportion, did the water which moistened the general soil contain too large a proportion of it in solution: if a plant languishes when it has not enough of one or other of its natural saline constituents, it also dies when furnished with the same substance in excess. 460 Let us now remember that salts can only act on vegetables in the state of solution, and we shall understand how those only which are but sparingly soluble, can ever be advantageously employed in agriculture. Water, in fact, having the power to dissolve only a very limited quantity of the mineral manure, will present it to the growing plant nearly in a constant quantity, so long as the soil contains any fair proportion of the substance. It is in this way precisely that gypsum appears to gain its superiority over the generality of mineral or saline manures; water does not take up more than th 1_th part of its weight before it becomes saturated; a certain proportion of the moisture of the earth being dissipated by evaporation, there is forthwith a precipitation of sulphate of lime; but the moisture that remains is nevertheless charged as before, neither more nor less, and in the fittest state, as it seems, to administer to the wants of the growing plant. If instead of sulphate of lime we suppose some salt that is much more soluble, sulphate of soda for example, we have nothing of the same state of equilibrium between the quantity of moisture and its charge of saline ingredients maintained. Supposing the moisture of the ground to holdth of sulphate of soda in solution, and this quantity calculated to produce good effects upon growing vegetables; suppose now that a drought sets in, which by dissipating one-half of the moisture, increases the charge of saline matter to th of its bulk, it may very well happen that this proportion, instead of proving beneficial, will be felt as injurious to vegetation. 1 330 The hypothesis of Davy, supported by these ingenious views of M. Chaptal, would therefore lead us to regard gypsum as behaving to plants in the same general way as the insoluble salts which usually form an element of the soil or of manures, the phosphate and carbonate of lime, in particular, salts which are made apt to enter the tissues of plants by the carbonic acid which is found in all the water that falls from the clouds and that moistens the soil, and which has the property of dissolving small quantities of them. But while the strength of these solutions, weak at all times, is liable through atmospherical vicissitudes to vary, when the mere traces of saline matter which at best they offer at any time are inadequate to meet the demands of a crop disposed to grow rapidly and luxuriantly, such as clover, sainfoin, and lucern, the solution of sulphate of lime, of the same strength at all times and under all circumstances, is ready to supply the plants with the mineral substance they require, however rapid and vigorous their growth. The theory of the action of gypsum proposed by Professor Liebig is extremely ingenious. He admits, with M. de Saussure, the presence of carbonate of ammonia in the atmosphere, and consequently in rain-water. This fact established, and it appears undeniable, the influence of gypsum would consist in its faculty of fixing the infinitely small quantity of carbonate of ammonia which is brought down by the rain and the dew, and so preventing its dissipation on the return of drought and sunshine. Carbonate of ammonia, in fact, as ve have already seen, when speaking of manures, in contact with the sulphate of lime decomposes this salt, carbonate of lime and sulphate of ammonia being formed. I shall by and by inquire whether the reaction that takes place is of the precise nature of that here stated; but admitting, for the present, that it is, it would still be competent for us to ask if the quantity of ammonia condensed in this way was likely to suffice for the production of such decided effects as we frequently witness in connection with the crops that are assisted by gypsum. Professor Liebig observes that a pound of sulphate of lime once converted into sulphate of ammonia, would introduce into the soil a quantity of ammonia equivalent to that which would be afforded it by 6.250 lbs. of horse's urine; a showing upon which it would be easy to demonstrate, taking the composition of sainfoin to be as I have shown it, that a pound of plaster fertilizing the ground to this extent, would be adequate to increase one hundred-fold the quantity of dry fodder produced. According to my manner of viewing this question, it must be examined on a totally different basis. It is certain, for instance, that gypsum has no effect upon natural meadows; positive experience has satisfied me of the absolute inutility of the substance here; so that upon my natural meadows at Bechelbronn, I now never employ a particle of it. But let us review Professor Liebig's theory in connection with the production of sainfoin and clover, which in a general way derive an advantage from gypsum, which no one disputes. Our harvest of clover, taken as dry, amounts on an average from strongly gypsed land, to 2 tons 1 cwt. very nearly per acre; and this quantity agrees pretty well with that which appears common in Germany. It is generally allowed that by gypsing we double the produce. It would follow from this, that an acre which had not been gypsed, would yield no more than 20 cwts. of dry clover; in my opinion the reduction would be still greater. Dry clover hay, made from the plant cut when in flower, contains about 2 per cent. of azote. The 20 cwts. of forage gained by the intervention of the gypsum would consequently contain 110 lbs. of ammonia, equivalent to 134.2 lbs. carbonate of ammonia. This consequently is the quantity of carbonate of ammonia which the gypsum ought to have been the means of procuring from the rain which falls upon an acre of land during the time that clover is upon the ground, in order to furnish the azote contained in the increased quantity of the crop. Now in Alsace, from the time of gypsing in April, to the time of mowing in July, there falls on an average 3.92, nearly 4 inches of rain, which would amount in round numbers to 982 tons per acre. Were the azote of what may be spoken of as the surplus produce, derived from the rain in fact, all the water that falls ought to contain 17000 of its weight of carbonate of ammonia. It is very questionable, however, whether any such proportion of ammoniacal salts exist in rain-water; yet the proportion ought to be very much greater, inasmuch as we have supposed the whole of the rain that fell to penetrate the ground, none of it to run off; but the truth is, that a very considerable proportion of the rain that falls never sinks into |