340 
TUH GEOLOGIST. 
ii'oiistono is absent, and a thick 
covering of drift lies on the 
Chalk ; and at such a spot as 
this Mr. Hariis made his large 
trench, described in Mr. Prcst- 
wicli's paper (p. S22). His 
smaller trench was dug at a spot 
(like that at C H), where a rem- 
nant of the ironstone remained 
tinder the drift. At H G is a 
peak of chalk standing high up 
in the Drift, which may be sup- 
posed to be thirty feet thick ; 
such rough pillars of chalk are 
not uncommonly met with in the 
excavations wliich the farmers 
make in gravel and clay to get 
chalk for their lands along the 
back of the North Downs. 
Mr. Prestwich truly states that 
it is difficult to trace at the sm'- 
face the range of the " Kentish 
Crag ;" and that it is so the 
diagram will show. It is but 
seldom that the u'onstone and 
ironsands are well seen at the 
surface ; they are usually masked 
by the Drift ; and further, these 
are but relics of the original 
beds ; and it is often difficult to 
distinguish these, even when ex- 
posed, from the ferruginous Drift 
in which they are enveloped. 
It is to be hoped that local 
observers will follow up Mr. 
Prestwich's researches, and en- 
deavour to work out more par- 
ticulars about these interesting 
u'onsands ; and perhaps the ac- 
companying diagram will serve 
the Jim-pose of connecting toge- 
ther before the eye the various 
conditions under which patches 
of these strata remain on the 
chalk-surface, and help to direct 
renewed attention to the subject. 
