CHAP. vri. A GREAT SAFETY -VAT.VE. 153 



of communication witli lower regions, filled with incandescent if 

 not molten lava, glowing and burning ; with flames travelling to 

 and fro over its surface, and scintillations scattering as from a 

 wood-fire ; lighted by tongues of flickering flame which issued 

 from the cracks in the surrounding slopes. 



At intervals of about half an hour the volcano regularly 

 blew off steam. It rose in jets with great violence from the 

 bottom of the crater, and boiled over the lip, continually envelop- 

 ing us. The noise on these occasions resembled that which we 

 hear when a large ocean steamer is blowing off steam. It 

 appeared to be pure, and we saw nothing thrown out, yet in 

 the morning the tent was almost black with matter which had 

 been ejected. These intermittent and violent escapes of (com- 

 paratively) small quantities of steam proceeded with considerable 

 regularity during our stay on the summit, but I cannot suppose 

 they are continually happening. They can scarcely have occurred 

 when we saw the clouds of steam quietly simmering out of the 

 crater from the Hacienda Kosario (see p. 123), or from our camp 

 upon Feb. 17, and upon numerous other occasions. My prede- 

 cessors on Cotopaxi do not speak of them. They were evidently 

 of the same nature, though much inferior in force to those 

 which we had seen emitted from Sangai a few weeks previously. 



I do not feel able to frame an explanation which would 

 account for these outbursts if it is assumed that fluid, molten 

 lava filled the pipe. I conjecture that the lava in the pipe 

 leading from the bottom of the crater, although intensely hot, 

 was cooling and settling down, closing fissures and imprisoning 

 steam that desired to escape, which presently acquired sufficient 

 force to burst through the barriers and effect temporary relief. 

 I imagine that the settling and closing-up process recommenced 

 after each outburst, until some unusually violent explosion estab- 

 lished what may be termed a free vent. The steam then welled 

 out unimpeded, in the manner we so frequently observed. After 

 such occasions, the internal pressure being diminished, I presume 



X 



