GEOLOGY AND MINERALOGY. 
65 
formed. It is not unreasonable to conclude that, long ere fiery 
vapour and lavas began to belch forth from the Sandy Bay crater, 
or the work of building up the Island commenced, this spot, where 
now simply a mountain stream trickles over the cliff falling in 
showers of spray to the bottom, was the site of a Solfatara of 
no moderate size and force, emitting water, aqueous vapour, and 
other gases, unaccompanied by the ejection of lava, cinders, or ashes. 
Such being the case, the discharge of steam and water must have 
continued with great force until after the lavas and other matter 
ejected from the Sandy Bay crater, which was distant three and a 
half miles south-westerly from it, had built up the Island to a 
height of a thousand feet or more above the level of the sea, each 
flow of lava northwards being checked in its course and so flowing 
round the watery discharge of the Solfatara. At a subsequent 
period, perhaps after the Island had been built up to its full height, 
this Solfatara or fountain of steam, probably at a time of its 
minimum power, became choked hy an accumulation of fragments of 
rocks and other debris ; and to its imprisoned force, struggling to 
obtain an outlet, may be attributed that shattering of the whole 
Island, which resulted in the upheaval of its northern portion, and 
the numerous rents across it, which being subsequently filled with 
lavas from below formed the various dikes we now see traversing 
ihe Island in the same direction as the line of upheaval — viz., from 
north-east to south-west. Although the large bowls at either end 
°t this line of upheaval — the one situated at Turk’s Cap Bay and 
the other at Manatee Bay — are very crateriform in appearance, there 
are no traces of lava strata which by their position can be said to 
have come from them. 
Turk’s Cap Valley, as it is called, lying between The Barn,Gregories, 
a nd Deadwood plain, presents an interesting part of the Island. From 
Deadwood it is easiest of access. Walking being out of the question, 
°ne has to slide down a number of deep furrows or narrow valleys 
°nt in the ochres and variously coloured clays for near two thousand 
feet, in order to reach the bottom. The furrowed and rugged surface 
°f these steeps is intersected in every direction with dikes of all sizes. 
I noticed some of them less than two inches wide, while others are as 
large as three or four feet in thickness. In almost every case they pre. 
Se nt marked instances of vitreous edges, showing plainly that they 
' Vere formed after the mass in which they occur had cooled. In this 
