The Active Volcano on Tanc, Keiv Hehrides. 77 



or 600 feet above the crater, fallino- back into it auain, or 

 earned by the wind over the leeward edge. The clouds of 

 steam and smoke generally assume a globular form, and 

 carried away by the wind, distribute upon the space over 

 which the}'^ pass quantities of fine volcanic dust. 



Accompanied by Mr. Neilson, I visited the crater, and 

 spent some time in watching the phenomena of its eruptions. 

 It was difficult, however, under the circumstances to make 

 calm and i-eliable observations. The noise was so appalling 

 and the situation so unusual and exciting that one could 

 well be pardoned for not collecting nuich accurate and 

 reliable data. The eruptions were too close also to be 

 studied properly, and the general impression received was of 

 a simultaneous explosion, earth tremor, and projection high 

 into the air of a torrent of stones, lava and smoke. 

 Between these principal explosions however, molten lava 

 occasionally surged up in the vents, accompanied by small 

 explosions and the ejection of fragments to a short distance 

 around, very much as is described as occurring at Stromboli in 

 the Mediterranean. Tlie diffei'ent vents appeared also to 

 exhibit a certain variety in their action, one of them throwing 

 the lava higher and with a loud explosion, the other throwing 

 up the larger masses with a less degree of force, as if they 

 tapped the reservoirs beneath at points of different pressure. 



2nd. — The Violent State. 



At certain periods the volcano becomes more than usually 

 active, the eruptions being not only more frequent, but more 

 forcible. A greater quantity of material is ejected, and it is 

 thrown to a greater height, much of it falling outside the 

 crater, and rolling down the sides. Referring to this state 

 Ml'. Neilson writes : — " Its period diminishes sometimes 

 to 4<5 or 50 seconds, and during rainy and thundry-looking 

 weather, it will thud away for a fortnight or three weeks at 

 this rate, shaking the whole island at every explosion and 

 being heard to a distance of 50 or 60 miles away. 



Mr. Forster, the companion of Captain Cook, more than a 

 century ago, noticed that rainy weather increased the violence 

 of the eruptions, and so did Mr. Brenchly in 1 865, I observed 

 that the rapidity and violence was increased not only when 

 the weather grew sultry, and bad weather approached, but 

 also durino" rain and for a short time after rain. 



