88 



PEOCEEDTNGS OF THE GEOLOGICAL SOCIETY. 



[Dec. 19, 



stiff whitish clay, wholly unstratified, containing much chalk debris 

 and occasional quartzose erratics. Its appearance is so like that 

 of the Bonlder-clay (No. 7 of figs. 2 & 3) which caps the high land 

 on each side of the valley, that but for its position it could not be 

 distinguished from it. It occurs at a slight elevation from the bot- 

 tom of the valley, resting on the chalk, and is from 9 to 15 feet in 

 thickness. In one part of the pit it is capped by laminated sands 

 and clays, which since their deposition have been subjected to dis- 

 turbance and denudation, as represented in the accompanying section. 



Pig. 1. — Section exJiibitecl hy the pit at Trowse Junction, being that 

 shown below the Railivay EmbanTcment in Jig. 2. 



1. Chalk. c. Laminated blue clay, passing up 



a. The clay. into 



b. Yellow sand, passing up into d. Yellow sand. 



e. Warp. 



In May 1866, Mr. Searles Y. Wood, Jun., while examining the 

 country for the purpose of tracing the extension of the ChiUesford 

 beds in this district, discovered a still more extensive development 

 of what I believe to be the same deposit, about three miles further 

 down the valley, near the Lunatic Asylum, and within a few hun- 

 dred yards of the well-known Thorpe crag-pit. In this case there 

 are no laminated beds overlying it, and the clay is of a somewhat 

 darker colour ; but in other respects it corresponds with that of the 

 last section, resting as in that case on the chalk, and but slightly 

 elevated above the level of the Eiver Yare. Not only is there here 

 a large pit where the clay is exposed, but the turnpike road is cut 

 through it for some distance. 



Pigs. 2 and 3 will show the position of the deposit relatively to 

 the other beds of the district. 



It will be observed that, in fig. 3, the Boulder-clay No. 7 is not 

 represented as occurring on the north side of the valley, its place 

 being supplied by the coarse plateau gravel No. 8. This gravel ex- 

 tends for some miles over what is known as Mousehold Heath, a pla- 

 teau to the north-east of Norwich, forming a sheet, in places, from 

 15 to 20 feet in thickness. It has apparently been formed by the 

 destruction of the Boulder-clay No. 7. That the Boulder-clay No. 7 

 formerly existed on this side of the valley is shown by the presence of 

 outliers further to the east. One of these outliers (that at Strump- 

 shaw) is overlain by the gravel No. 8. 



If these sections be correct, it will appear that the deposit treated 



