1452. The deterioration of the British climate is an idea entertained by some; but, whether in regard to general regularity, temperature, moisture, or wind, the alleged changes are unsupported by satisfactory proofs. It is not improbable but the humidity of our climate, as Williams alleges (Climate of Britain, &c., 1816), has of late years been increased by the increase of evaporating surfaces, produced by the multiplicity of hedges and plantations; a surface covered with leaves being found to evaporate considerably more than a naked surface. If the humidity of the climate were greater before the drainage of morasses and the eradication of forests for agricultural purposes, a comparative return to the same state, by artificial planting and irrigation, must have a tendency to produce the same results. However, it will be long before the irrigation of lands is carried to such a degree as to produce the insalubrious effects of undrained morasses: and as to our woods and hedges, we must console ourselves with the beauty and the shelter which they produce, for the increase of vapour supposed to proceed from them. Many arguments in favour of the belief that a change has taken place in the British climate, have been drawn from old books on horticulture, in which seeds are directed to be sown at seasons when we know they would now perish; and fruit is said to ripen in months when it is now never ripe. In Evelyn's Sylva, published in 1664, we are informed that cherries, strawberries, &c., were ripe in the open ground in May; raspberries, corinths (currants), melons, &c., in June; and peaches, nectarines, and plums, in July and August; and even after making allowance for the fact that, before the change of style, May extended to what is now the middle of the second week in June, we shall find that these fruits are now full a fortnight or three weeks later in ripening than they were in Evelyn's time. Some curious remarks on the change of climate in Britain during the last thirty years of the eighteenth century may be found in Garnett's Tour through the Highlands of Scotland in 1800, and in Pinkerton's Geography, vol. i. p. 70. Both these writers assert that the British climate is now more cold and moist than it was formerly; but in an article in the Edinburgh Review, vol. xxx. p. 1., on 'Polar Ice, and a North West Passage,' it is asserted that no material change has taken place in the climate of Europe for the last 1000 years.
