256 An Essay on the medical Effects of Cttmates. 



advantages over London with respect to equability of cli- 

 mate, if we judge of tiie ciunate of London from the ob- 

 servations made at the apartments of the Koyal Sociity 

 only: but in so central a situation, tlic changes must be 

 rendered much less sensible by the eflcct of the surrounding 

 buildings; and they appear to be considerably greater at 

 Gravesend, and greater still at Knightsbridge. In this re- 

 spect, too, Penzance retains its superiority even over Devon- 

 shire. Lisbon seems to have a less variable temperature 

 than any part of Great Britain; and in Madeira, to judge 

 by the monthly variation only, the advantage in this re- 

 spect appears to be still greater. 



The greatest possible equability of temperature seems 

 however to be obtained in a sea voyage to a warm climate, 

 in which the variation seldom amounts to half as much as 

 in the most favourable situation on shore, even on a small 

 island ; and in pulmonary cases, the motion of a ship would 

 probably in general be rather beneficial than otherwise, 

 while the fatigue of travelling in bad roads, and the danger 

 of sleeping in damp beds, present an alternative by no 

 means favourable to a journey by land. 



The direction of the wind alone can seldom have any im- 

 mediate eflfect on the salubrity of the climate, except by 

 variously modifying its temperature, according to the seas 

 or countries over wliich it blows. There is a method of 

 computing the mean direction of the wind, which does not 

 appear to have been hitherto adopted, but which affords a 

 very simple and intelligible result, although somewhat la- 

 borious if extensively applied. U consists in finding the 

 bearing and distance of a point, to which a light body 

 would be carried by the wind in the course of the year, 

 supposing the velocity to be constant, wheii its variations 

 have not been ascertained by observation. It is obvious 

 that the bearing of such a point will show at once the mean 

 direction of the prevalent winds ; and its distance, com- 

 pared with the effect of a constant wind for the same time, 

 as a unit, will indicate the degree in which those winds 

 have prevailed. 



Prevalence of Winds. 



London, 1790-4 VV". g** S. -234. 



London, 1794 W. 33" S, 'ISS. 



Dawlish, 1794 W. 6° S. •4G(5. 



Lisbon, 1788 N. rW.-SlS. 

 According to this comparison, it appears that the meaa, 

 direction of the wind in Devonshire is somewhat more 

 westerly than in London : and thai the degree, in which 



such 





i4^^. ' 



