VESUVIUS. 187 



through a great arched chasm in the side of the moun- 

 tain. It flowed with the clearness of ' honey in regular 

 channels, cut finer than art can imitate, and glowing 

 with all the splendour of the sun. Sir William 

 Hamilton had conceived,' adds Dr. Clarke, ' that 

 stones thrown upon a current of lava would produce 

 no impression. I was soon convinced of the contrary. 

 Light bodies, indeed, of five, ten, and fifteen pounds' 

 weight, made little or no impression, even at the 

 source ; but bodies of sixty, seventy, and eighty 

 pounds were seen to form a kind of bed on the surface 

 of the lava, and float away with it. A stone of three 

 hundredweight, that had been thrown out by the 

 crater, lay near the source of the current of lava. I 

 raised it up on one end, and then let it fall in upon 

 the liquid lava, when it gradually sank beneath the 

 surface and disappeared. If I wished to describe the 

 manner in which it acted upon the lava, I should say 

 that it was like a loaf of bread thrown into a bowl of 

 very thick honey, which gradually involves itself in 

 the heavy liquid, and then slowly sinks to the bottom.' 

 But, as the lava flowed down the mountain slopes, 

 it lost its brilliant whiteness ; a crust began to form 

 upon the surface of the still molten lava, and this 

 crust broke into innumerable fragments of porous 

 matter, called scorise. Underneath this crust across 

 which Dr. Clarke and his companions were able to 

 pass without other injury than the singeing of their 

 boots the liquid lava still continued to force its way 

 onward and downward past all obstacles. On its 



