Tlie Geology of the Loivev Lei<jli Valley. 93 



With regard to the relation of the lower basalt to the miocene, 

 the evidence is conclusive. There are many sections showing 

 the former rock with eocene strata directly underlying, but 

 nowhere is there a trace of the miocene conglomerate in a similar 

 position. On the contrary, it is invariably the superior rock. 

 That it is in immediate contact with the upper eocene limestones 

 is plainly demonstrated iu several sections, but it also frequently 

 transgresses beyond them, and then rests on the basalt. In all 

 probability the volcanic rock was once entirely covered by the 

 conglomerate, from which it has been in part removed by 

 fluviatile action. 



The cross section shown in the plate is intended to illustrate 

 the supposed relation, on the theory just stated, of the lower 

 volcanic to the eocene and miocene strata. If this approximately 

 represents the disposition of the rocks below the surface, it is 

 plain that in an eroded gully there may be limestone cropping 

 out at a higher level than the basalt, though the latter is a 

 subsequent deposit. The surface outline of the section is con- 

 structed from observations on the right bank of the river below 

 Shelford. 



In endeavouring to trace the course of the lower basalt in the 

 gorge of the Leigh, we will start from the north, as it has 

 apparently flowed in a southerly direction. Only the ruins of 

 the flow are in reality now present, a great part of it having 

 been undoubtedly disintegrated and carried away by the action 

 of the river. There are several prominent rocky eminences 

 close to the bed of the river, the most notable of which is Dog 

 Island. Another is known locally as Rocky Castle, and a third 

 as Point Henry. Other minor knolls exist also here and there, 

 one or two of which we have incidentally referred to before. 

 Messrs. Etheridge and Murray, in speaking of these basaltic 

 outliers, recognise that they mark the course of a lava flow, 

 though the question as to whether it is distinct or not from that 

 on the plains is left untouched. We quote their remarks in 

 full: — " From the southern boundary of Quarter-sheet 26 S.E., 

 down the valley of the Leigh, a series of small elevations occur 

 in the bed of the river, of which the Dog Island is the most 

 conspicuous. This is a small hill rising abruptly from the 

 alluvial flat ; it is capped by a layer of basalt about ten feet 



