61 



Or even after the volcano had lost the power to eject? It is 

 a remarkable fact that whilst the lava field lies immediately 

 under the shadow of the mountain it is almost entirely free 

 from ash deposits. The absence of such deposits cannot be re- 

 ferred to erosive effects, as the area contains a great many 

 deep depressions between the walls of lava, which, on such a 

 theory, ought to have been the receptacles of the ash, but they 

 do not contain it, supplying the inference that no great amount 

 of ash could have been thrown out from the crater subsequent 

 to the outbreak of the lava at its foot. 



On the other hand, a section supplied in the walls of the 

 little lake, which exists immediately at the base of the Mount 

 on its western side, shows the ash deposits entirely superior 

 in position to the lava flow. This small depression, for such it 

 is, is at a lower level than the present bottom of the cratjr, 

 which accounts for the fact that whilst the latter is dry, the 

 small outside depression has water in it, shaving sunk below 

 the water level of the district. Around the greater portion 

 of this lake there are vertical walls of Eocene limestone, like 

 those encircling the Valley Lake and the Blue Lake at Mount 

 Gambler. A thin layer of the old surface soil can be noted 

 as resting on the limestone rock, hardened and discolored by 

 the proximity of the igneous sheet which immediately overlies 

 it. The lava at this point is for the most part compact in 

 texture, but on the western side of the depression it is more 

 vesicular, and in stalactitic forms, probably indicating the 

 line of Assure at which the igneous matter reached the sur- 

 face. This is still further rendered probable in that no lime- 

 stone is seen in situ at this particular spot, having presumably 

 been disturbed and removed by the intrusive rock. As already 

 stated, the ash beds in this section entirely overlie the lava 

 flow, and if they exist in their natural position must demon- 

 strate that this particular sheet of lava was fed from a fissure 

 that probably existed before the tufaceous cone was built up. 

 It is possible, however, that the ashbeds, now covering the lava 

 sheet, may be the effect of a rearrangement of material. The site 

 is at the base of the cone, which rises immediately above it at 

 a high angle, and it is not improbable that the scour of the side 

 may have brought down tlie loose material on to the lava floor, 

 producing a secondary series of deposits. If this was the 

 source of the ashbeds, such rearrangement of material must 

 have taken place before the depression of the lake occurred. 



The evidence supplied by the great north-west ridge, des- 

 cribed above, is more definite. There we have the igneous 

 rock penetrating and distorting the volcanic tufa, demonstrat- 

 ing the anterior age of the ash. The same thing is proved 

 by this fissure originating some distance up the side of the vol- 

 canic cone, and on which the lava is dependent for support. 



