Masterpieces of Science 



ally, each puff giving rise to clouds which shoot 

 up to a great height, and are- either dissipated 

 or condensed in torrents of rain. Associated 

 with the steam are various gaseous exhalations, 

 mpst of which, however, are not combustible. 

 Hence, the appearance of a column of flame, 

 often said to be seen issuing from a volcano, 

 must generally be an illusion, due to illumination 

 of the vapours, partly by the sparks and red-hot 

 stones and ashes shot out at the same time, and 



FIG. 51. Diagrammatic Section of a Cinder Cone 



partly, by reflection from the glowing walls of 

 the pipe and from the surface of the molten 

 matter below. In the early stages of an erup- 

 tion, huge fragments of rock may be ejected; 

 for when, after a period of repose, the pent-up 

 steam and gases at last gain vent, they violently 

 eject the materials which have accumulated in 

 the throat of the chimney, and choked its opening. 

 Masses of rock, some as much as nine feet in 

 diameter, are said to have been cast forth from 

 the great volcano Cotopaxi, in Quito, during the 

 eruption of 1553, and to have been hurled to a 

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