clover roots increase in size much more than when fed, and so afford greater nourishment to the wheat."

Voelcker further observes, (Jour. Roy. Ag. Soc., vol. iv. N. S. p. 397,): "Whilst it holds good as a general rule that no soil can be cropped for any length of time without gradually becoming more and more infertile, if no manure be applied to it, or if the fertilizing elements removed by the crops grown thereon be not by some means or other restored, it is nevertheless a fact that after a heavy crop of clover carried off as hay, the land, far from being less fertile than before, is peculiarly well adapted, even without the addition of manure, to bear a good crop of wheat in the following year, provided the season be favorable to its growth. This fact, indeed, is so well known that many farmers justly regard the growth of clover as one of the best preparatory operations which the land can undergo in order to its producing an abundant crop of wheat in the following year. It has further been noticed that clover mown twice, leaves the land in a better condition as regards its wheat-producing capabilities, than when mown once only for hay, and the second crop fed off on the land by sheep; for, notwithstanding that in the latter instance the fertilizing elements in the clover-crop are in part restored in the sheep excrements, yet, contrary to expectation, this partial restoration of the elements of fertility to the land, has not the effect of producing more or better wheat in the following year than is reaped on land from off which the whole clover crop has been carried, and to which no manure whatever has been applied. Again, in the opinion of several good practical agriculturists with whom I have conversed on the subject, land whereon clover has been grown for seed in the preceding year, yields a better crop of wheat than it does when the clover is mown twice for hay, or even only once, and afterwards fed off by sheep.

"Most crops left for seed, I need hardly observe, exhaust the land far more than they do when they are cut down at an earlier stage of their growth; hence, the binding clauses in

most farm leases, which compel the tenant not to grow corn crops more frequently, nor to a greater extent than stipulated. However, in the case of clover grown for seed, we have, according to the testimony of trustworthy witnesses, an exception to a law generally applicable to most other crops."

The elaborate investigations of the Professor are well worthy of the careful study of the agriculturist, since they materially tend to the elucidation of a very serious difficulty. The result of these long-continued labors rather inclines to the conclusion that it is the large amount of nitrogen, accumulated in the soil by the clover plant, that renders it afterwards so well adapted for the growth of wheat, and that the explanation of the phenomenon must not be sought in the amount of mineral matters required by either the clover or the wheat.

This conclusion might, perhaps, have been anticipated, by the fact well known to the agriculturist, that nitrogenous manures are commonly far more beneficial to wheat than those of a mineral or saline nature; and hence, also, we are led to strongly incline to the opinion that the clover plant possesses a power of assimilating nitrogen from another source than from the soil.

I can only give in this paper a brief quotation or two, explanatory of the results obtained by the Professor, referring to the last published number of the Journal of the Royal Agricultural Society for far more complete and valuable details.

The first question to be decided was the amount of mineral matters abstracted from the soil by the wheat and clover crops, and thus ascertain if the explanation of the mystery was to be found in the results of the analysis. On this considerable branch of the inquiry the Professor remarks:

"By those taking a superficial view of the subject, it may be suggested that any injury likely to be caused by the removal of a certain amount of fertilizing matter is altogether insignificant, and more than compensated for by the benefit which results from the abundant growth of clover-roots and the physical improvement in the soil which takes place in their

decomposition. Looking, however more closely into the matter, it will be found that in a good crop of clover-hay a very considerable amount of both mineral and organic substances is carried off the land, and that if the total amount of such constituents in a crop had to be regarded exclusively as the measure for determining the relative degrees in which the different farm-crops exhaust the land, clover would have to be described as about the most exhaustive crop in the entire rotation.

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Clover-hay, on an average, and in round numbers, contains in 100 parts:

"The mineral portion, or ash, in 100 parts of clover-hay,

"Let us suppose the land to have yielded 4 tons of cloverhay per acre. According to the preceding data, we find that such a crop includes 224 lbs. of nitrogen, equal to 272 lbs. of ammonia, and 672 lbs. of mineral matter or ash constituents. "In 672 lbs. of clover-ash we find

"Four tons of clover-hay, the produce of one acre, thus contains a large amount of nitrogen, and remove from the soil an enormous quantity of mineral matters, abounding in lime and potash, and containing also a good deal of phosphoric acid.

"Leaving for a moment the question untouched, whether the nitrogen contained in the clover is derived from the soil or the atmosphere, or partly from the one and partly from the other, no question can arise as to the original source from which the mineral matters in the clover produce is derived. In relation, therefore, to the ash-constituents, clover must be regarded as one of the most exhausting crops usually cultivated in this country. This appears strikingly to be the case when we compare the preceding figures with the quantity of mineral matters which an average crop of wheat removes from an acre of land.

"The grain and straw of wheat contain in round numbers in 100 parts:

"The ash of wheat contains in 100 parts:

"The mean produce of wheat per acre may be estimated at 25 bushels, which, at 60 lbs. per bushel, gives 1,500 lbs.; and

as the weight of the straw is generally twice that of the grain, its produce will be 3,000 lbs. According, therefore, to the preceding data, there will be carried away from the soil :

"On the average of the analysis, it will be found that the composition of these 175 lbs. is as follows:

Soda, chloride of sodium, oxide of iron, sand, &c..... 0.5 lbs.

"The total quantity of ash-constituents carried off the land in an average crop of wheat, thus amounts to only 175 lbs. per acre, whilst a good crop of clover removes as much as 672 lbs.

Nearly two-thirds of the total amount of mineral in the grain and straw of one acre of wheat consists of silica, of which there is an ample supply in almost every soil. The restoration of silica, therefore, need not trouble us in any way, especially as there is not a single instance on record proving that silica, even in a soluble condition, has ever been applied to land with the slightest advantage to corn or grass crops, which are rich in silica, and which, for this reason, may be assumed to be particularly grateful for a supply of it in a soluble state.

'Silica, indeed, if at all capable of producing a beneficial effect, ought to be useful to these crops, either by strengthening the straw or stems of graminaceous plants, or otherwise benefiting them; but after deducting the amount of silica from the total amount of mineral matters in the wheat produce of