142 
A. E. SALTEE-THE GEAYELS 
Up to the present we have been dealing with deposits made up 
jnainly of local material with a fair amount derived from the 
Triassic or older strata, the only igneous rocks met with being 
of a rhyolitic type. 
On the highest parts of the Chalk slope east of the Dunstable 
Downs, excluding Warden Hill, a totally different class of deposit is 
found. It is largely made up of clay, but contains numerous frag¬ 
ments of rocks derived from a distance, which in places form beds 
of gravel. They can be studied at Great Offley 526 ft. O.D. 
and at Gravel Hill 500 ft. O.D. on the top of the escarpment 
south of Hexton. At West Mill just below 300 ft. O.D., 
south of Buntingford, there is a deposit 10 ft. thick containing 
much non-local material probably derived from higher deposits. 
At that station the deposit is stratified in places, and is made up 
of flints, Chalk pebbles, gryphseas, belemnites, large and small, 
coprolites from the Cambridge Greensand, Bed Chalk, hard chalk, 
sandstones, quartzites, Carboniferous Limestone, Carboniferous 
chert, etc. A. block of'basalt 12 ins. by 8 ins. was seen in situ , 
and a sandstone boulder 12 ins. by 12 ins. Close by, near the 
Fever Hospital (Mr. B. Shepheard’s pits), and nearer Aspenden, 
similar deposits may be seen. 
At Offley, in a pit 10 ft. deep at the back of Mr. Charles Forster’s 
house near the windmill, many erratics were found during a recent 
visit, including rhomben porphyry, two or three varieties of basalt, 
Carboniferous Limestone, GrypJtcea incurva and dilatata , large belem¬ 
nites and other Jurassic debris, quartz-pebbles, red and other 
coloured quartzites, and dark chert. Flints were numerous and 
pebbles of hard chalk were present. The patch on Gravel Hill 
was of a similar character, but I did not see any igneous rocks. 
Associated with these deposits are many large boulders of 
igneous and other rocks. These may be seen by the roadside, etc., 
at the following places:—Upper Sundon and Streatley, Beds; 
Wallington near Church, Cumberlow Green, Sundon, Kelshall, 
Boe Green, between Beed and Barkway, and West Mill.* Deposits 
at lower levels show by their constituents that they have derived 
their non-local material from the higher gravels. The large 
gravel-pits near Leagrave and Limbury, north of Luton, Beds, 
at 400 ft. O.D., contain much material derived from higher 
deposits like those of Offley, etc.f At Hatfield Hyde two boulder- 
clays may be seen separated by a bed of gravel .J 
As the gravel deposits described in 2 and 3 are free from the 
non local material peculiar to the deposits here described, it seems 
reasonable to suppose that these latter were deposited subsequently 
* H. G. Fordham, “Botes on Boulders and Boulder Clay in North Hert¬ 
fordshire,” ‘Trans. Herts Nat. Hist. Soc.,’ Yol. Ill, p. 33; J. Y. Elsden, 
“ On the Microscopic Structure of Boulders found in the North of Hertfordshire,” 
lOC. Cttm p, 47* 
f Cf. also “ Geology of South Beds,” J. Saunders, ‘ Geol. Mag.,’ 1890, p. 122. 
X Cf. ‘Trans. Herts Nat. Hist. Soc.,’ Yol. X, p. xxviii, and ‘ Proc. Geol. 
Assoc.,’ vol. xv, p. 308. 
