594 ADDITIONAL NOTES.

of calcareous lime with foil, he found that thirty or forty grains of lime did not retard the growth of feeds more than three or four of calcined magnefa; from hence what can we conclude? but that, as they both injure vegetation in large quantities, they may both afkft vegetation in fmall ones? and that this is more probable, as the far- mers believe, that they find both of them ufeful, though in different quantities; and as the magnefia would form Epfom falt, if it meets with vitriolic acid, which Dr. Home found from his experiments to be friendly to vegetation, when ufed in very fmall quantities. More accurate obfervations and more numeérous experiments on this fub-

“ca are required, which this important difcovery of Mr. T'ennant’s will I hope foon occafion.

13. To be inferted at p. 286, 1. 16, at the end of No. 2 of Seët. XI.

Another method has been attempted by fome for the purpofe of ameliorating clayey lands, which were unfit to be turned up deeper than they had been accuftomed to be ploughed, on account of their acidity or tenacity being very injurious to vecetation; as the wbite faggar clays over many coal countries; or fome very tenacious red clays, which may contain à vitriol of iron; not an oxyde, or oxy- senated calx of it.

The method 1 allude to confifis in firft turning over a ridge of

earth, as in common ploughing; and then with a plough, made on

purpofe, to peunetrate{orne inches deeper into the clay fo injurious to vegetatiOn; this plough 1s to be fo contrived, as to raife up the clayey foil about the bréadth of the furrow recently made, and three or four inches deep, or more; but not to turn it ovér, fo that it may {till lie under the fertile foil, which is to be turned over it with the common plough, in making the adjoining furrow,. So that this

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