AXD BAGSHOT BEDS OP AXDEBSHOT. 



433 



Mr. Irving in his paper refers to the green sands of the Middle 

 Bagshot as occurring at the foot of the northern slope of Caesar's 

 Camp at an altitude of 350 feet. This is 50 feet higher than the 

 top of the Middle Bagshots, as he shows them by his pebble-bed in 

 the railway-cutting. To produce this a synclinal flexure is neces- 

 sary having its axis in Aldershot town, of which we have no proof. 

 As in fact these green sands are at an altitude of 450 feet, a still 

 sharper bend must be supposed if we admit the Thorn-Redan Hill 

 anticlinal. 



Again, the green sand in situ occurs at from 500 to 550 feet in 

 Coesar's Camp and Hungry Hill ; and this, coupled with the fact that 

 the Middle-Bagshot beds can be traced from the Canal across the 

 Long Yalley up into the flanks of Caesar's Camp, points to a regular 

 northerly dip. 



Now, turning to the same section as drawn by Messrs. Monckton 

 and Herries, we find that, too, to be slightly misleading, though they 

 indeed show the persistent northerly dip of all the beds which, I 

 have shown, is most probable. The difference in level shown 

 between Thorn Hill and Redan Hill is the cause of this ; for, as 

 Thorn Hill is 100 feet above the valley, one would assume from the 

 section that Eedan Hill was 30 feet below the opposite hill, whereas 

 it is in reality but one foot below it. Again, from the figuring and 

 description of the section, I understand that the authors consider 

 the pebble-bed to represent the Middle Bagshot, and refer all below 

 it to the sands of the Lower Bagshot, omitting the Middle Bagshot 

 clays which occur below the pebble-bed in Thorn Hill in the well- 

 borings and all the surface-sections about, and cap Redan Hill below 

 the gravel. 



I will now shortly show how the section in fig. 1 was drawn 

 from the evidence brought forward. 



The form of the ground having been plotted from the 6" Ordnance 

 Survey map of 1882, the pebble-bed was put in as follows : — Below 

 the point marked 362 feet, which is the Time-gun, the bed is 

 exposed at 300 feet by the Magazine, a point at right angles to the 

 line of section and 400 yards distant, in an exposure by the Cemetery, 

 and one on the pathway below the Mortuary Chapel : and from these 

 three points, between which the bed can be traced continuously, the 

 line of division between the Upper and Middle Bagshots is drawn. 



The thickness of the Middle Bagshot is given by the well-section 

 quoted on p. 434, and by the outcrop of clay-beds on the two hill- 

 slopes from which it was plotted, and found to coincide with the 

 well-section. The London Clay I believe to crop out as shown, as 

 there are two ponds of water lying in this hollow, and the clay is 

 shown in the brickfield on the hill above, where it is overlain by a 

 few feet of Lower Bagshot loam. This also coincides with the well- 

 section. In this section it will be seen that I agree with the Survey 

 mapping, except that I take the top of Bedan Hill to be Middle 

 Bagshot, having the whole thickness of the Lower Bagshot beneath 

 it. The Cambridge Hospital and South Camp are shown in elevation, 

 with the pebble-bed forming the surface of the ground. 



