126 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



a degree with the sandstones of the Bagshot Sands. As usual with 

 concretionary masses, they occur in patches in particular districts, and 

 are far from being a general accompaniment of the sands. In Hamp- 

 shire I know only of one group of them which has the appearance of 

 being in situ, — the one before referred to (p. 81 ) as occurring near Dor- 

 chester*. Still the case there is not clear. In the western part of 

 the London tertiary district the middle division of the Lower Tertiaries 

 always contains more or less extensive beds of quartzose sand, with 

 patches or layers of pebbles in the lower part more especially of the 

 group, while patches of subangular flints are also occasionally met 

 with; consequently we have the elements necessary to produce the 

 required results whenever circumstances, as might so easily happen, 

 occurred to consolidate the materials. Although instances of this fact 

 are not numerous, still they are in sufficient number to prove the pro- 

 bability of the supposition. 



On the eastern slope of Bagshot Hill, near Hungerford, there is a 

 spot from which blocks of sandstone and of sandstone conglomerate 

 have been removedf . This pit, which is now abandoned, is so shallow 

 as not to show the superposition of the beds : they appear, however, 

 immediately to overlie the chalk. The case is clearer at Nettlebed 

 Hill ; I have there seen, a few feet above the chalk, blocks of sand- 

 stone, some of large size, in situ in the sands interstratified with the 

 mottled clay (see fig. 4. p. 89). 



At Tiler's Hill near Chesham the white quartzose sand underlying 

 the Basement-bed of the London clay contains a thin subordinate 

 band of a soft saccharoid sandstone. Near Batler's Green, two and a 

 half miles northward from Elstree, Herts, there existed a few years 

 since a shallow pit, in which beneath the gravel there was exposed a 

 surface of thick tabular pudding-stone overlying the chalk and ap- 

 parently in situ. A bed perfectly identical in composition, i.e. con- 

 sisting of a fine pure white quartzose sand full of black flint pebbles, 

 but not consolidated, was opened a few years ago in a pit one and a 

 half mile from Ware, on the London road : it was 3 feet thick, re- 

 posed directly on the chalk, and underlay some sandy mottled clays. 

 Blocks of sandstone and of sandstone conglomerate are also found in 

 the sands subordinate to the mottled cla3's beneath the London 

 clay at Pinner (see p. 91). These cases are few and local, but so 

 also is the distribution of the greyweathers themselves, and it is to 

 be observed that the occurrence of the latter is exactly coincident 

 with the development and preponderance of the sand beds of the 

 mottled clay series. Thus around Reading, where mottled clays 

 preponderate, there are few sandstone blocks on the surrounding 

 chalk hills ; but in proceeding towards Newbury the clays give way 

 to sands, which, three miles north of that town, constitute the main 



* In Hampshire the Bracklesham series contains several soUd seams, both in 

 the Isle of ^Yigbt and the Isle of Purbeck, yet but few blocks are found scattered 

 on the surface. The chief one is that known as the Agglestone, near Studland. 



t I am indebted for a knowledge of this locality, and for much other informa- 

 tion respecting Salisbury Plains and the Wiltshire Downs, to Mr. \V. Cunnington 

 of Devizes. 



