Having detailed the general results of the experiment, I beg to offer the following remarks upon some points in it, which seem to me to require a little elucidation.  I consider the success of this experiment to be in a great measure owing to the use of soluble silica and magnesia; because, although there is an abundance of silica in the soil, my first crop showed very miserable results, the grain being ill-fed and poor, and the straw soft and discoloured, although the year 1842 was, in this district, very favourable for wheat, the month of August being singularly fine and warm; but when I combined the nitrate of soda with sulphate of magnesia, as in experiment No. 1 in 1843, but still more so when I combined it with the silicate of soda, as in No. 3 of that year, the straw became as strong, firm, and bright as need be desired; and this year when both these salts are combined with nitrate of soda, common salt, and gypsum, I have not only good and bright straw, but also an abundant crop of wheat.

With respect to the lime used, it may be as well to state that the field had not been limed for many years, and although in a limestone district, showed a deficiency of lime on analysis.  The soil is a strong loam, on a brick clay subsoil, in which there is little or no lime, although the stony clays, which form the subsoil in a great part of the district, abound in it, containing from twenty to thirty per cent. of carbonate of lime.  I had always believed that lime was used in great excess in this neighbourhood, and had, in fact, an idea that its good qualities were overrated, inasmuch as it does not enter into the composition of the plant, except in very minute proportion; but last winter I saw a paper (by Mr. Briggs of Overton) on the possibility of growing wheat on the same land year after year, in which the utility of lime in preventing rust was incidentally touched upon.  I also saw Liebig’s letters explaining the action of quicklime in liberating potash from the clay; and then I considered it very important to ascertain the proper quantity to be applied.  The quantity required to decompose the phosphate of iron was not great, and assuming Liebig’s theory of its action in liberating the potash to be true, it seemed to me that an excess of lime would permanently impoverish the land; for, supposing that the crop required 100 lbs. of potash, and as much lime was applied as liberated 500 lbs., what became of the 400 lbs. which did not enter into the composition of the plant? was not a large portion of this 400 lbs. washed down the drains by the rain, and so lost for ever?  Perhaps the absence of lime in this field accounts for its beneficial action in the experiment just detailed; but if my supposition is correct, that any excess of potash which may be liberated from the clay by the use of quicklime (that is, any more than may be required to perfect the crop), is washed down the drains, and thus the land is permanently impoverished by the excessive use of lime, it behoves