402 TRANSACTIONS OP SECTION 0* 



of Miocene age ; Hohenbocka sand, of the same age, containing carbonaceous 

 layers; Fontainebleau sand, in Upper Oligocene deposits, with lignites; Inferior 

 Oolite sands in the Yorkshire and Northampton districts, containing planty 

 matter and roots; Burythorpe sand (Callovian), containing carbonised woody 

 material and peaty matter ; Aylesbury and Leighton Buzzard sands (Lower 

 Greensand) with peaty bands ; Headon Hill and Bagshot sands from Alum 

 Bay, Wareham, and other places (Eocene, &c.), interbedded with lignites. 

 Numerous other examples may be adduced. Attention may also be drawn to 

 the very pure sandstones of the Coal Measures, associated with coal-seams, and 

 to the white sandstones found with the Brora coals of Scotland (Callovian). 

 The bleaching of the reddish sands for a foot or two in depth upon our heaths 

 is a similar phenomenon. In each case the freedom from iron may be attributed 

 to the reducing action of the planty matter, in changing the ferric salts to the 

 more soluble ferrous state, when they are more easily removed by percolating 

 waters. 



The beds of white sand seem always to be of limited thickness, and 

 frequently to be laid down under lagoon or estuarine conditions favouring the 

 development of plant life. 



Cementation is objectionable, either because of the introduction of impuri- 

 ties or because of the cost of subsequent crushing. It is desirable, however, 

 that the deposits should be incoherent. The most widely-used sands are thus 

 of comparatively late geological age. Most of them occur in Tertiary deposits, 

 but some are Cretaceous in age. A strong tendency also exists for the simplifica- 

 tion in mineral constitution, (due to elimination of more easily decomposable 

 minerals) and greater perfection of grading in the later geological sedimentfi^ 

 a result of their constituents having passed through many geological cycles. 



3. Report on the Lower Carboniferous Flora at Gullane. 

 See Reports, p'. 217. 



Interim Report on the Old Red Sandstone Rocks of Kiltorcar 

 Ireland. — See Eeports, p. 205. 



Report of the Geological Photographs Committee. 

 See Reports, p. 218. 



