WEST INDIAN VOLCANIC ERUPTIONS 



21 I 



the right bank of the stream, an explosion suddenly took place, 

 continuing with the usual attendant phenomena of "ash-geyser" 

 eruptions. The explosion dug the bank rapidly away, adding 

 the erupted detritus to the dam, which by rising increased the 

 supply of water and the force of the explosions. Eventually 

 the lake overflowed and a channel was cut back which, draining 



B.oUf|ooJ|>U ,| H 



^3ecfei°>>- li».rouoK. an,A&h.-^g^/ser'Coaa. 



Fig. 8. 



it by this outlet, brought a cessation of the eruption. The water 

 may reach the hot-ash bed by filtration through the overlying 

 deposit, or by pouring down the pipe or chimney when the ori- 

 fice lies submerged. 



Description of secondary cones. — The effects of these eruptions 

 within the river courses simulate those of true volcanic craters. 

 Steam rushes up through the overlying beds, carrying with it 

 fragments from below and from the surrounding walls. It 

 throws ejecta, composed of fine and coarse fragments (some 

 were the size of a man's head) , to a considerable height (that of 

 a mile being observed), the finer material being doubtless 

 scattered to distances of miles, but the coarse falling within 

 the immediate vicinity of the vent. By gradual accumulation 



