53-2 TROI'ILM. IIYCIEMi. SAMTATIOX, RTC. 



from (»nc jjlact* to another with a incin tempera lure of considerable 

 variation must be done at intervals. 



Health resorts can be found in the troi)ics at hij^jh altitudes. 

 It is useful to know that approximately the temjierature decreases 

 1° F. for everv ,V)() ffet of heij^'ht, or i° C\ for every iSo metres, hut 

 here aLfain if the mean average temperature is much lower than that 

 of a previous residence, sick people must approa( h it j^Madually, in 

 stages, no matter how beneficial that altitude may be. This has been 

 manifested verv forcibly during the late war in connection with 

 aviation. When aviators move very rapidly through varying atmo- 

 spheric pre.ssures there are such results produced upon the vital organs 

 of the bodv that only selected persons can become aviators. 



Atmospheric pressure is much less on the equator than about the 

 parallels of Cancer and Capricorn, because the constant heating of 

 the air, more or less loaded with a(|ueous vajxiur, ascends to high 

 altitudes with considerable force. This expansion and rising of air 

 is followed bv an inrush of cool air from the north and south to fill 

 the space, hence if heat were universally uniform there would not be 

 any winds. The currents of air on either side of the equator, not 

 across the ocean, meet at the ef|iiator and produce calms or 

 " doldrums." 



The easterly direction of winds is due to the rotation of the earth. 

 The air over the land is heated more rapidly than that over the sea, 

 hence the land air rising is replaced by the cooler moist sea air, and 

 is known as the " sea breezes." At night the land, having given off 

 its heat verv rapidiv, is cooler than the sea, hence the conditions are 

 reversed and we get " land breezes," when wind comes from the land 

 to the sea. Hence the pre.sence of large tracts of water have a cooling 

 inlluence over the adjacent, land. 'J'he land breeze, being dry, is apt 

 to extract too much moisture abruptly, and cau.ses a cooling process 

 which may cau.se serious chills and .so reduce one's resistance to 

 disea.se. 



The \.I{. and .S.W. nionscrons of India are explained by Dove as 

 follows: Owing to the heating of the great plains of .Asia, where the 

 air ascends during the months from May to .\iigust, the south-east 

 trade wind, which is blowing .south from the equator, is drawn north- 

 wards, at the .same time being deflected to the west, thus forming the 

 .S.W. mon.soon. Conversely, when the plains cool from November 

 to March, there is a breeze from the north-east towards the equator 

 which, though known as the X.F.. mon.soon, is really a trade wind. 

 The .S.W. mon.soon is laden with moisture. .\ failure of the rain 

 from this monsoon means a .serious Indian famine accompanied by 

 tens of thou.sands of deaths. 



