1879.] Various Altitudes on the Island and Peak of Teneriffe. 501 



a height of 8,900 feet. (P. Smyth — Teneriffe — an Astronomer's 

 .Experiments.") 



Although my first station was 1,810 feet below that at which 

 Piazzi Smyth's observations were made, I cannot think the direct 

 solar heat was notably less. 



I procured at Puerto a large box, and had it perforated with 

 many holes on every side to allow of free access of air into it. 

 This box was used as a screen for my thermometers ; if I mistake not r 

 a similar plan had been adopted by Professor Smyth. The screen 

 was placed under my wooden shed, and thereby sheltered from the 

 sun. While on my Alpine stations, I was working under a mean 

 temperature of 89° at St. Theoclule, and 52° and 43° at the Riffel and 

 St. Bernard respectively, my atmospheric temperature on the Peak of 

 Teneriffe was from 65° to 69° in the shade, and rose in the sun much 

 higher than on the Alps ; in fact I was throughout the day time 

 exposed to a climate much warmer than at my Alpine stations ; so 

 far, therefore, my object, in going to Teneriffe, of avoiding cold at 

 comparatively great altitudes above the sea was attained. 



3rd, Moisture. — The great dryness of the air in the daytime was 

 very remarkable, the total mean difference between the dry and wet 

 bulb readings at Guajara (7,090 feet) being 25°*6, and at Alta Yista 

 (10,700 feet) 19°*7; while at Puerto de Orotava, at the seaside, the 

 difference fell to 8° "7. I was never conscious of perspiring, and my 

 skin was always very dry, with the throat parched at times. The 

 evaporation from the skin must have been very great so high above 

 the sea, in such dry air and under so powerful a sun. 



The inquiry may be divided into three parts : The first refers to- 

 the respiratory phenomena at the various stations while in the sitting- 

 posture. The second, to the respiratory phenomena observed while 

 engaged upon a definite amount of muscular work. The third, to 

 the amount of watery vapour expired sitting at my different stations* 

 I shall beg to commence with the experiments relating to the breathing 

 while in the sitting posture. 



The method adopted in these experiments was precisely the same 

 as that I had made use of in the Alps, with this very slight difference, 

 that instead of cooling the air expired into the bag, to the temperature 

 of the water in the aspirator, where it was treated with the solution of 

 barium, I noted the temperature of the air in the bag immediately 

 after filling it, and drew the air at once from the bag into the 

 aspirator or tube, recording its temperature in the tube. In nearly 

 every case the temperature in the tube was rather lower than in the 

 bag, so that a contraction took place ; the degree of contraction was 

 duly taken into account in the calculations of the analysis. I also 

 used common water instead of a solution of salt for aspiring the air 

 for analysis into the tube. 



