Page:Transactions of the Provincial Medical and Surgical Association, volume 4.djvu/226

 124 times the thermometer, at night, falls several degrees lower in the plain than at Malvern, particularly if the atmosphere is calm: an evident indication that moderate elevations are much less subjected to the effects of terrestrial radiation than places lower down. The houses at Malvern appear to lie between those fogs which result from the cold of radiation, and those descending from above; and, speaking from my own observation, I should remark, that they are oftener enveloped in the latter species of fog than the former. When the lower edge of a cloud descends so as to obscure objects raised only 500 or 600 feet above the mean level of the earth's surface, the barometer will generally be found low, and the temperature, except, perhaps, in the summer months, above the mean of the season; so that these may truly be called warm fogs, in contradistinction to those which rise upward by the gradual thickening or deepening of the cold misty, and too often malarious, stratum below.

The salubrity of Malvern may, I think, be attributed,—first, to the air being rendered pure and invigorating by an elevation sufficiently above the cold and miasmatous strata caused by terrestrial radiation;—secondly, to the dry sandy nature of the soil, resulting from the decomposition of the contiguous rock;-thirdly, to the shelter from easterly winds especially, afforded by the precipitous rise of the hill in close contiguity to the habitations;—and, lastly, to the extreme purity of the water, and the beauty of the scenery around.