suppose it would have no excrements? Let this be applied to plants: are we to suppose that the plant assimilates all that is absorbed by its roots and leaves? When that which is absorbed is what would enter into the composition of the plant, is it not more rational to suppose that the inorganic and gaseous constituents only combine in fixed proportions, and that although the plant may absorb a much larger proportion of one than is required, the surplus is discharged excrementitiously, and perhaps may be unfitted for entering into the plant until it has undergone a decomposition? In conclusion, I trust you will pardon my frankness in so boldly canvassing your opinions; but it is in this collision of opinion that the truth will be elicited, and if I judge you aright, it is that you wish to discover whether it harmonizes with your preconceived notions or not. * * * * * LOW MOOR, _1st May_, 1845. HENRY BRIGGS, ESQ. I duly received your pamphlet on the use of lime, for which I am much obliged, and am delighted to perceive that you confirm the idea (expressed in my pamphlet on the growth of wheat every year on the same land) that the excessive use of lime is ultimately injurious to the fertility of the soil to which it is applied. This, coming from a gentleman of your reputation and experience, will, I hope, induce someone capable of performing the experiment to endeavour to ascertain with precision how much lime it is desirable to apply to an acre to give the best results, and with the least waste, assuming that the land contained little or none previous to the experiment; and it would also be desirable to ascertain whether it is better, in an economical point of view, to apply a small quantity every year, or a larger quantity every third or fourth. My own opinion is in favour of the former method, except that it is difficult to get it ploughed in, particularly in wet weather, immediately after spreading (which is essential where you grow wheat on the same land every year) without injuring the feet of the horses. You speak of ten days or a fortnight being necessary to neutralize caustic lime, but our horses had their feet injured by it six weeks after it had been spread on the land, last year, although the weather had been wet almost the whole of the time, say from the beginning of February to the middle of March. You appear to think that lime will replace silica in the wheat plant. Whose authority have you for this? It will be very important to establish this supposition, but I fear it is too good news to be true. On referring to your letter, I find you don't say what I supposed you did, but that the lime liberates the soluble silicates, potash, &c. This may be, and certainly the beneficial effects of lime in growing wheat are not to be explained by any other hypothesis with which I am acquainted. I am this year trying some experiments to ascertain (if I can) the cause of clover- sickness, and I hope to be in a position to say whether your