242 THE GKOLOOIST. 



gravels of the London district, is seldom to be determined ; the cutting 

 itself throws no light on this subject, or, at least, nothing very definite. 

 33ut a ballast pit has recently been opened at the Watford end of the 

 Bricket T\^ood cutting, and immediately south of the line, '^vhich exposes 

 a section of much interest. The Eoulder Clay has there almost thinned 

 out, leaving but a seam one to two feet thick, whilst both above and 

 below it is a thick bed of gravel. The lower sandy gravel, which con- 

 sists chiefly of sub-angular flints and flint pebbles, Avith some quartz, 

 sandstone, and old-rock pebbles, with subordinate seams of whitish sand, 

 has a clean, washed appearance. The upper gravel consists of very simi- 

 lar sub-angular materials, but is less sandy and darker in colour; arising 

 apparently from the admixture of clay derived from the wearing down 

 of the Boulder Clay. The upper gravel seems to be of limited extent, 

 but the lower gravel I believe to pass under the Boulder Clay, for 

 there is an old pit of the same gravel near the brook on the north side 

 of Bricket Wood, towards the AYatford end. There is no Boulder Clay 

 in this other pit, but the gravel presents the peculiarity of being con- 

 creted in places into large brecciated and sandy masses by a 

 calcareous cement. In this pit I found no organic remains ; 

 but in the ballast pit I Vvas fortunate enough to discover, in the lower 

 gravel, a few pieces (but not suflicient to determine the species) of the 

 tooth and tusk of an elephant. A workman, whom I afterwards spoke 

 to on the common, told me he had found several bones in the lower 

 part of the gravel, but none of them had been preserved. The lower 

 gravel reposes upon an. irregular surface of chalk, v/hich is exposed 

 at places at the bottom of the pit, which is now no longer worked 

 and may, I understand, possibly soon be levelled. Tt is well worth a 

 visit, and a longer search than I have been able to give. There is a 

 station at Bricket Wood, but it is at the St. Alban's end of the wood, 

 ht a considerable distance from this cutting. 



