Probable Miocene Age of Conglomi rate, Shelford. 179 



which is approximately to scale. The elevations are from 

 aneroid observations of our own, and the distances of the stations 

 on the hillside have been measured for us by Mr. Swan. 



At the particular portion of the river bank where the conglom- 

 erate appears, the eocene beds are not visible, but we consider 

 ourselves justified, from evidence obtained at other portions of 

 the gorge, in assuming their existence here, and at no great depth 

 beneath the basalt ; at the base of the section they may indeed 

 be somewhat more deeply seated than the drawing indicates, 

 while the outline of their surface farther in the hill is of course 

 uncertain. North of Shelford, outcrops of the strata also occur, 

 but generally reaching a higher level on the banks, and an uneven 

 surface is thus indicated, which points to erosion before the out- 

 flow of the lava took place. In the section figured, the basalt 

 appears first at a height of fifty feet above the water's edge, and 

 our conclusion that it is there in situ is confirmed by the fact 

 that the eocene strata of the Red Bluff, a mile and a half down 

 the stream, are covered by lava at about the same elevation. 

 Going still farther up the hill, a moderately deep quarry in solid 

 basalt is 110 feet above the same datum line. Beyond this 

 quarry and at a height of 145 feet above the river level, the first 

 block of the conglomerate in situ was observed. A few scattered 

 pieces were found on the surface a little lower down, but they 

 have probably come from above. The fossiliferous boulders can 

 be traced up the hill from this point for a distance of about 150 

 yards, and for thirty-five feet in vertical elevation, or to a height 

 above datum line of 180 feet, when they cease, and the only 

 stones cropping out higher up belong to the prevailing lava flow. 

 By a farther i*ise of forty feet in a distance of 137 yards, the 

 summit of the western bank of the river gorge is reached, its 

 total height being thus 220 feet. The distance from the water's 

 edge to the level country bounding the gorge is 766 yards, so 

 that the slope, like that on basaltic banks generally, is a gentle 

 one. On the east of the river there is an extensive flat before 

 the corresponding rise commences, but the aneroid recorded 

 almost exactly the same elevation for the top of the bank on 

 that side, and we may therefore conclude that the lava once 

 spread as a level sheet right aci'oss the present gorge, which has 

 been since excavated to the depth mentioned. 



