Senry Woodward — On Vohanos. 341 



30° from the Equator, but to this rule tliere are exceptions ; for amid 



Arctic and Antarctic snows blaze forth — 



JanMayen, at the North Pole 6,874ft. 



Hecla in Iceland, „ 5,110 



Mount St.. Elias, North America 17,860 



Kamtschatka, in North Asia 15,763 



Taranaki, New Zealand, in the South Sea 8,840 



New South Shetlands, „ „ 



St. Paul „ „ 



Erebus, Antarctic 12,400 



The products of volcanic action are most various,^ and are either 

 thrown into the air by the explosive gases and vapours which ac- 

 company a volcanic eruption, and fall as dust, ashes, scoria, and 

 stones; or are poured out in a stream of melted rock from the 

 summit, or more generally the flanks of the volcano. 



In consequence of the explosive force being directed nearly verti- 

 cally, and the ashes falling on all sides equally round the aperture, 

 the hills of scoria, ashes, etc., accumulated round a volcanic vent are 

 always conical. Whether lava-currents issue from the apex or the 

 side, they merely cause a slight irregularity in figure; but a new 

 explosive vent, opening towards the base of the mountain, may 

 throw up a new hill (see Fig. 4, p. 342). Thus several cones on 

 the flanks of ^tna have been thrown up in the Val del Bove, a great 

 excavation in the side of its cone. 



Fig. 3. — Cone of Cotopaxi; seen from a distance of 30 miles. 



The cone of Cotopaxi (18,875ft. in height above the sea), in the 



1 The following gaseous and other products have been observed as emanating from 

 volcanos : — 



Steam. 

 Hydi'ogen. 



Sulphuretted Hydrogen. 

 Sulphurous Acid. 

 Carbonic Acid. 

 Nitrogen. 



Chloride of Sodium. 

 Chloride of Potassium. 

 Chloride of Ammonium'. 

 Sulphur. 



Ashes. 



Pumice. 



Sand. 



Lapilli. 



Scorise. 



Bombs. 



Vesicular Lava. 



Obsidian. 



Basalt. 



