CHAP. in. SANGAI IN ERUPTION. 75 



ceased^ and the steam-cloud lias formed ; and, in C, this cloud is 

 being carried to leeward, and is melting away. Sometimes these 

 clouds drifted ten or twelve miles before they were dissipated, 

 and as a rule they had quite disappeared before a fresh outburst 

 created a new one. 



Three points of interest in connection with these outbursts of 

 steam may be mentioned. 1. The rapidity of the ejection. This 

 can be estimated with some probability, as our position was nearly 

 on a level with the summit of Sangai, and was favourably situated 

 for observation. The part of the cone within sight was about 

 4000 feet high ; the jets rose to about once and a half this height, 

 in less than three seconds, and they were consequently projected in 

 the air at the rate of about twenty-tico miles pe7^ minute. 2. The 

 cloud formed by the steam took the shape of ordinary cumulus, 

 rudely flat below, and piled up above. This was repeated time 

 after time. 3. The drift of these clouds southwards demonstrated 

 the existence of a current of air, 22-23,000 feet above the sea, 

 directed from north to south. From our small number of observa- 

 tions, it would be rash to conclude that this current is a permanent 

 one, although from subsequent experiences it would appear that 

 it exists during a considerable portion of the year. 



The 6th of January commenced with fine weather, and I 

 went again with the Carrels to the foot of the Southern Walls. 

 This time we ascended the 1243 feet in 88 minutes. The lower 

 cliffs (marked D on the sketch plan of Chimborazo) are not so lofty, 

 or as perpendicular as the upper series, and (if provided with ice- 

 axes) one can traverse the slopes underneath them without much 

 trouble, though they are steep and have many streaks or sheets of 

 ice caused by the refreezing of the water which trickles off the 

 rocks. There is evidence that a certain amount of liquefaction 

 goes on even at the top of Chimborazo (notwithstanding the low 

 mean temperature that prevails there) in the enormous icicles 

 which depend from the lower surfaces of the coronal glacier. 

 Some were fully one hundred and fifty feet long. 



