82 PHENOMENA OF DRY ATMOSPHERE. 



" is at this season almost unknown, except in the badly 

 ventilated houses." * 



On the great table lands of the Andes, in Peru and 

 Bolivia, beneath the rays of a tropical sun, these 

 extreme variations of temperature are, as might be 

 expected, even still more extraordinary. 



" In May and June (their winter months) at midday in the 

 shade there is an average temperature of 55 Fahr., and dur- 

 ing the rest of the year of 64 Fahr., but in the sun of 110 

 and upwards. This great disparity between the temperature 

 in the shade and in the sun, is everywhere met with on 

 elevated table lands, at a height of more than 10,000 feet : 

 and is explained by the rarefication and dryness of the at- 

 mosphere, which unlike damp air, is unable to retain and 

 diffuse solar heat, whether on its passage from the sun or 

 reflected from the ground." f 



Speaking on this same subject, Dr. Tucker Wise 

 observes that 



" It is remarkable what misunderstanding prevails on 

 the subject of humidity in relation to equability of climate. 

 Books are written, extolling certain places as being ' dry and 

 equable.' It is not too much to say that there is no climate 

 on the face of the earth which is ' dry and equable.' Nearly 

 every climate which has a small range of temperature is 

 necessarily a moist one, for it is the alternate evaporation 

 and condensation of moisture which limits the range of the 

 thermometer." 



We must next consider the influence of the winds 

 as a factor in the determination of climate. 



Some writers have even (and as we believe rightly) 



*. Alpine Winter in Its Medical Aspects, by A. Tucker Wise, M.D., 

 Third Edition; p. 98 (Pamphlet, no date). 



j" Stanford's Compendium of Geography and Travel for Australia 

 and South America, edited by H. W. Bates, 1878, p. 207. 



Alpine Winter in Its Medical Aspects, p. 41. 



