languid than on drier lands. They will also be particularly important in accounting for the opposite effects which take place in the autumn, and at the approach of winter: nay by such alone, I conceive, can we assign any probable cause why calcareous and sandy soils which had previously exhibited greater fertility by earlier vegetation than clayey or deep ones should at that season so notoriously manifest a greater decline of vegetative power.
"On the same principle too, I would explain a fact, probably not generally noticed, though rather anomalous in the science of vegetation: it is, that meadow or pasture grounds which have been covered with water during a part of the winter, on being drained even early in the spring will for a short time shew a verdure which the adjoining drier lands cannot equal; when afterwards, on the continued action of the rays of light, the dry lands will far surpass them. This I beg to be understood as confined to land which had been covered with water not of a fertilizing quality; not such as having passed through a highly cultivated country might deposit its sediment.
"Nor will this principle be found less useful in accounting for the different effects which a sudden change in the heat of the atmosphere may produce on certain vegetables, in different or even on the same soils when under other modes of management. Whatever has a tendency to check a quick and great loss of temperature in the substances which surround such vegetables, particularly their roots, will be best calculated to save them from that effect and from vegetative death; consequently those earths which are the worst conductors of heat, or in other words, are the longest in heating and cooling, will be the most favorable in resisting any sudden alteration, and the vegetables growing on them will be the least injured when so assailed."
After all, evaporation is the great generator of cold, and although there may be some intrinsic and original difference in the capacities of different earths for retaining heat, abstracted from the retention of water, Mr. Egremont cannot avoid concluding, it is to that retentive power that the chief cause of difference is assignable, and that soils are good and bad conductors of heat according to the moisture they contain. The inference is that clay, being of all others the most retentive, will defend crops from the mildew better than drier soils: and allowance being made for local differences, that soils most liable to have their crops injured may be stated in the following order: Peat or moor, calcareous, sand, grey earth, and clay.
That the susceptibility of these soils to injury from mildew is actually diminished in the order here laid down is a hazardous statement: next to peat or moor, my observation justifies me in suspecting that strong, adhesive, clayey soils, especially those which
