174 ReviewH — W. Johnson's Wimbledon Common. . 



book should prove a delightful companion. But readers of this 

 Magazine in particular will be glad to learn that fully one-third 

 of the book is devoted to the geology and physical geography of 

 the Common. This is probablj* the best part of the book, and, 

 together with the chapter on the Common in prehistoric times, bears 

 witness to the most intimate personal knowledge and study. There 

 are various geological problems connected with Wimbledon Common, 

 but the most important of these and the most difficult to solve is the 

 age of the large sheet of gravel to which it owes its existence. 

 After discussing the various theories with full reference to other parts 

 of the Thames Valley, and after describing in detail the various 

 sections to be seen on or near the Common itself, Mr. Johnson 

 concludes that " the precise age of the gravels must frankly be 

 left undecided. That they are river-gravels belonging to a date 

 anterior to the formation of the Second or 100-foot Terrace may 

 be considered certain", and Mr. Jolinson is inclined to think that 

 they are of slightly earlier origin than those of Dartford Heath, 

 and that they were deposited contemporaneously with the Boulder 

 Clay or possibly earlier. Shortly afterwards the plateau was raised, 

 never again to be covered by water. This view agrees in the main 

 with that of Messrs. Hinton and Kennard, and, so far as evidence 

 from Wimbledon Common itself goes, I am aware of nothing to 

 contradict it. It may, however, be worth adding to Mr. Johnson's 

 account of the constituents of the gravel that rather large flints, some 

 white-skinned, some cavernous, appear to be less rare than is usual 

 on the Common itself in a high-lying gravel-])it on the Peek Estate 

 close to Peek Crescent, now closed to the public. The most 

 interesting stone that I have yet found on Wimbledon Common 

 came from a pit near that named E by Mr. Johnson. It is a piece 

 of white quartzite, measuring about 3x2x1 inches. It appears 

 originally to have had a somewhat rectangular outline, but one 

 surface is gently rounded and water-worn, while the other surface 

 has been ground smooth and nearly flat except for broad, shallow, 

 almost imperceptible furrows running across it, and is remarkably 

 suggestive of glacial action. The exterior of the pebble has the 

 usual reddish-brown stain of the gravel, and where a piece has been 

 broken off, probably by frost, along pre-existing cracks, the interior is 

 seen to be much paler. The interesting feature of the rock is that 

 it is full of the external moulds and imprints of small cylindrical 

 crinoid columnals, with cylindrical lumen and well-marked radiating 

 ridges on the joint-faces. Within two days of my finding this, 

 chance placed in my hands a piece of closely similar rock labelled 

 " Halkin Burr". And I imagine that both specimens represent 

 a Carboniferous sandstone such as is found in Flintshire. Among 

 the constituents of the Wimbledon gravel, Mr. Johnson mentions 

 "many discoidal cakes of pale-grey sandstone". These seem to 

 belong to a different rock from the "red ferruginous grit", which 

 he also mentions, but he does not discuss their origin. Are they not 

 fragments of Sarsen stone ? 



In almost every exposure on Wimbledon Common and in the 

 neighbourhood, the gravels are underlaid by sands resting on the 



