BY T. W. EDGEWORTH DAVID. 427 



and a few hundred feet below the summit a small sheet of 

 laminated or vertically jointed andesite lava is observable dipping 

 at a somewhat steep angle off the central axis of the mountain. 

 This lava is traversed by such numbers of vertical joints and set 

 so closely together as to present the appearance of being a mass 

 of slate. Microscopic examination, however, proves it to be 

 identical, or nearly so, in composition with the rest of the ande- 

 sitic lavas of this locality. Its specific gravity is 2-462. 



At a point bearing about S. 15°., W. 78 yards distant from the 

 Trigonometrical Station on top of the "Old Man Canobla," is 

 what the author considers to be the central " neck " of the volcano, 

 in the shape of a nearly circular mass of coarsely crystalline and 

 very dense andesitic lava, rising from four to five feet above the 

 general level, and showing strongly marked oblique lamination, the 

 laminae dipping in towards the centre of the neck at an angle of 

 from 40° to 60°. The neck is about | chain in diameter, and is 

 surrounded by beds of scoriaceous lava to the north and scorise to 

 the south. The beds of the former to the north dip northerly at 

 about 15°, and are overlaid by a dense flow of lava, on the highest 

 point of which the Trigonometrical Station now stands. 



South of the neck the beds of scoriae dip first northerly towards 

 the neck, then qua-qua-versally chiefly from west towards south 

 at an angle of from 20° up to 40", as far as the western edge of 

 the mountain, where the scoriae pass into a coarse volcanic 

 agglomerate composed chiefly of large pieces of cellular andesitic 

 lava. The southerly dip here probably represents the dip of the 

 beds on the outer slope of the old crater, while the northerly dip 

 towards the neck represents the crater-ward dip. 



A curious semi-circular hollow floored with dense lava is observ- 

 able a few chains south-south-westerly from the Trigonome- 

 trical Station, but in the present denuded state of this ancient 

 volcano it is difiicult without detailed mapping to ascertain its 

 exact relation to the central neck 



