276 VOLCANCITOS AND VEGETATION. 



nence of the ground. It was observed that when the 

 apertures, which are not placed at the summit of 

 the cones, and are enclosed by a little mud wall 

 from 10 to 15 inches high, are nearly contiguous, the 

 explosions did not take place at the same time. It 

 would appear that each crater receives the gas by 

 distinct canals, or that these, terminating in the 

 same reservoir of compressed air, oppose greater 

 or less impediments to the passage of the aeriform 

 fluids. The cones have no doubt been raised by 

 these fluids, and the dull sound that precedes the dis- 

 engagement of them indicates that the ground is 

 hollow. The natives asserted that there had been 

 no observable change in the form and number of 

 the cones for twenty years, and that the little cavi- 

 ties are filled with water even in the driest seasons. 

 The temperature of this liquid was not higher than 

 that of the atmosphere ; the latter having been 

 81-5°, and the former 80*6° or 81°, at the time of 

 Humboldt's visit. A stick could easily be pushed 

 into the apertures to the depth of six or seven 

 feet, and the dark-coloured clay or mud was ex- 

 ceedingly soft. An ignited body was immediately 

 extinguished on being immersed in the gas collected 

 from the bubbles, which was found to be pure azote. 



The stay which our travellers made at Turbaco 

 was uncommonly agreeable, and added greatly to 

 their collection of plants. " Even now," says Hum- 

 boldt, writing in 1831, " after so long a lapse of 

 time, and after returning from the banks of the Obi 

 and the confines of Chinese Zungaria, these bamboo 

 thickets, that wild luxuriance of vegetation, those 

 orchidese covering the old trunks of the ocotea and In- 

 dian rig, that majestic view of the snowy mountains, 

 that light mist filling the bottom of the valleys at 

 sunrise, those tufts of gigantic trees rising like ver- 

 dant islets from a sea of vapours, incessantly pre- 

 sent themselves to my imagination. At Turbaco 

 we lived a simple and laborious life. We were young ; 



