24 ABOUT VOLCANOS AND EARTHQUAKES. 



of St Januarius should be brought out and shown to the 

 mountain ; and when this was done, all the uproar 

 ceased on the instant, and Vesuvius became as quiet 

 as a lamb ! 



(33.) He did not continue so, however, and it would 

 have been well for Naples if the good Saint's head could 

 have been permanently fixed in some conspicuous place 

 in sight of the hill for from that time till the year 1779 

 it never was quiet. In the spring of that year it began 

 to pour out lava ; and on one occasion, when Sir Wil- 

 liam Hamilton approached too near, the running stream 

 was on the point of surrounding him ; and the sulphure- 

 ous vapour cut off his retreat, so that his only mode of 

 escape was to walk across the lava, which, to his aston- 

 ishment, and, no doubt, to his great joy, he found 

 accompanied with no difficulty, and with no more incon- 

 venience than what proceeded from the radiation of heat 

 on his legs and feet from the scoriae and cinders with 

 which the external crust of the lava was loaded ; and 

 which in great measure intercepted and confined the 

 glowing heat of the ignited mass below. 



(34.) In such cases, and when cooled down to a 

 certain point, the motion of the lava-stream is slow and 

 creeping; rather rolling over itself than flowing like a 

 river ; the top becoming the bottom, owing to the tough- 

 ness of the half-congealed crust. When it issues, how- 

 ever, from any accessible vent, it is described as perfectly 

 liquid, of an intense white heat, and spouting or welling 

 forth with extreme rapidity. So Sir Humphry Davy 

 described it in an eruption at which he was present ; 



