148 J. W. Judd — On Volcanos. 



in the calm and sultry weather of July, 1771, he visited the island, 

 and ascended to the crater. Then the slight ejections of stones, 

 which never rose more than 100 feet above the crater, while very 

 few of them fell outside its rim, took place at regular intervals of 

 seven or eight minutes; and the glow of light, above the crater was 

 seen only at the moment of the explosion, or for a few seconds 

 afterwards. 



In August, 1788, Spallanzani saw "the fires of Stromboli" at a 

 distance of 100 miles, the explosions at that time taking place at 

 very irregular intervals. On the 1st and 2nd of October, in the 

 same year, during very stormy weather, he found the eruptions of 

 the mountain were so violent, that the whole island and the sea 

 around were lighted up at times by them ; the houses were shaken 

 by the violent concussions of the air; and ashes fell in the inhabited 

 parts of the island, two miles distant from the crater. Yet the 

 islanders assured Spallanzani that much more violent outbursts 

 sometimes took place. On the 3rd of October, when the weather fell 

 calm, much slighter explosions Were seen to take place at intervals 

 of not more than two or three minutes. On the night of the 4th, 

 when Spallanzani visited the crater, the ejections were found taking 

 place in the same rapid manner, but with very varying degrees of 

 intensity. The account given by the great Italian philosopher of 

 what he witnessed within the crater is most graphic and interesting. 

 On its western side a very great number of fumaroles were seen dis- 

 charging jets of steam, while deposits of yellow salts were being 

 formed round their orifices ; but on its eastern side one large mouth 

 poured forth a continuous column of vapour, about 12 feet in dia- 

 meter. In the centre of the crater, however, still more striking 

 appearances were exhibited, for here a funnel-shaped tube was seen 

 containing liquid lava. This incandescent mass was agitated by 

 two movements, " one intestine, whirling and tumultuous, the other 

 that by which it was impelled upwards and downwards." This ver- 

 tical motion, the utmost range of which was estimated at 20 feet, 

 was sometimes slow, and at others more sudden ; but, on its reaching 

 a certain height, large bubbles were seen to collect on the surface of 

 the glowing mass, and these, bursting with a sharp report, carried 

 innumerable fragments of the liquid rock in a fiery shower into the 

 air. After the explosion, the lava was seen to sink again in the tube, 

 to recommence its rise after a short interval. On one occasion, how- 

 ever, Spallanzani witnessed a most interesting occurrence in the 

 crater of Stromboli : the lava sinking lower than usual in the tube, 

 while the fumaroles began to discharge with a deafening roar, their 

 orifices at the same time becoming red-hot. This striking pheno- 

 menon soon ceased, however, the noi*mal action of the crater being 

 resumed ; and Spallanzani was assured by his guides that this peculiar 

 condition of the crater only rarely occurred, and was never of long 

 duration. In connexion with this very remarkable circumstance, it 

 may be well to recall the fact that, during the recent eruption in the 

 crater of Vulcano, the fumaroles ceased to discharge, but that on its 

 termination their activity was renewed with greatly increased 

 violence. 



