An Essay on the medical Effects of Climatts. 211 



The simple indications of a thermoitieler, however accu- 

 rately they may be observed, in the most unexceptionable, 

 exposure, by no means afford a correct test of the tempera- 

 ture, as it affects the human system: nor is it possible to 

 express the modifications produced by wind and moisture, 

 even supposing them to be easily known, by any numerical 

 measure which shall be applicable to every relative situation 

 of the individual. I have known an atmosphere at 63°, 

 with a thick fog, and a very little wind from the N.E., ap- 

 pear, to a person taking moderate exercise, most oppressivHy 

 sultry ; although a person, sitting long still, might have felt 

 the same air uncomfortably cold. Moisture must make 

 both heat and cold more sensible ; the one, by diminishing 

 perspiration, the other, by increasing the conducting power 

 of air. Wind is doubly concerned in affecting the pro- 

 perties of a climate ; first, as the great cause crf preventing 

 a general accumulation of heat over considerable tracts of 

 country; and secondly, as having a similar effect with re- 

 spect to the immediate neighbourhood of the person ; and 

 its operation is as generally perceptible in the latter way, 

 where we have no precise mode of estimating its magni- 

 tude, as in the former, where it is corrtctly indicated by a 

 thermometer sufficiently exposed: although, in fact, the 

 most shaded fixed thermometer may often be observed to 

 indicate a temperature many degrees higher, than that of 

 the breeze which is circulating in the neighbouring country. 

 Still more commonly by the sea side, the wind c xhibits the 

 temperature of the water over which it has blown : at 

 Worthing it is seldom above 64" in the holiest Vveaiher, 

 although the sea, when the tide flows in at noon, .ver the 

 heated expanse of sand, is sometimes ra«sed to 78", where 

 it is several feet deep. 



To the inhabitants of these islands, ;he most important 

 properties of the climatesof other countries are those, which 

 render them more or less lit for the residence ot persons liable 

 to catarrhal or consumptive affections. Hence, w.irnuh and 

 equability of temperature, especially in the winter months, 

 are the first objects of our inquiry in ihc theoreiical com- 

 parison of climates. Moisture is supposed, bv some, to be 

 favourable, by others, to be unfavourable, to such persons : 

 it mav therefore be safely neglected, except as tending to 

 increase the evils depending on a want of eq. ability ot lem- 

 pci tturc. The effluvia of inoist ground are sufficiently wtil 

 known as the causes of paludal fevers; furthd' than this 

 they require no particular investigation. Nor can we at- 

 tempt to assign any reasorv for peculiarities, which render 

 O 2 »omo 



