APPENDIX A. 



ON THE FALL OF TEMPERATURE IN ASCENDING TO HEIGHTS 

 ABOVE THE SEA-LEVEL. 



The remarkable features of the climate of Western Peru referred 

 to in the text seem to me to admit of a partial explanation from 

 the local conditions affecting that region. The most important 

 of these are the prevalence of a relatively cold oceanic current, 

 and of accompanying southerly breezes along the Peruvian 

 coast. These not only directly affect the temperature of the 

 air and the soil in the coast-zone, but, by causing fogs throughout 

 a considerable part of the year, intercept a large share of solar 

 radiation. It has been found in Northern Chili, some fifteen 

 degrees farther south than Lima, but under similar climatal 

 conditions, that, although the land rises rather rapidly in 

 receding from the coast, the mean temperature increases with 

 increasing height for a considerable distance. It is stated on 

 good authority * that at Potrero Grande, a place about fifty 

 miles distant, and 850 metres above the sea, the mean annual 

 temperature is higher by 2'5° C. than at Copiapo, or at the 

 adjoining port of Caldera. It is probable that in the valley of 

 the Rimac the mean temperature at a height of 1000 metres is 

 at least as high as it is at Lima. Taking the mean temperature 

 of the lower station at I9'2° C, and that of Chicla at I2"2° C, 

 that would give a fall of 7° for a difference of level of 2724 

 metres, or an average fall of 1° for 387 metres, instead of 1° for 

 512 metres, as given in the text. 



A further peculiarity in the climate, which tends to diminish 



* I borrow this statement from the excellent " Lehrbuch der Klimato- 

 logie," by Dr. Julius Hann. Stuttgart, 1883. 



2 B 



