No. 111.
ON TIIK UF,l,.\TION.S OF OTHILH .SIMII.AU fiEOLOGICAL PII/ENOMENA.
the unilci'miniDg ngcnc:}- of lanii-sjirings npi)ears froiii the rorcgoing ncoouiils to plav so
••llioiciit a part among llii; ai;tiial causes which iiiodlfv the forai of the caith's surface, the qiieslioi.
may periiu,« suggest itself, whcllier it may not have hmx a coDcun-eat agent M.>tl, vokoi.ic
forces III producing similar dislocations In earlier geological jieriods; but it is clear lliat « e caii
only lock for l!ie traces of s.icl, a canse «-here tiie tmot aftectcd l.ad already emerged from the
level of the sea, and formed porliou of soineisland or continent. But the most marked geological
distilrhanCCS, (from the relations they bear to the hods uf congluineratc, once loose drifted shingle),
very generally appear lo ha> c been submarine, and therefore the eflcct of tlic volcanic forces
winch originally elevatcrl the continents. But no sooner had our contittenls assumed their pi-eseiit
general form, tlinn «"c may be sure that the cause wc kai-e now been considering begnu lo
act wherever tlie circumstances n-ere favourable, tliat is, wlierever the triple combiimtion of
Simla of i-oek sand and clay occurred. Wherever valleys of denudation were found skirled by
HMch materials, we may believe that events similar lo tliose recorded ut Lymne and near Selbonie,
must repeatedly liave formed on the brow of tlie escarpments of the hills abrui)t scars, beneath
which u rolling surjiico of subsided masse.s w.iuld extend towards the valley. The attention of the
wrllerof this Weniuir \r,is jxirlicuIarly called to this configuration as very generally prevailing in
tlie Vidlejs of Eastern Devon, by his frlen.i Professor Bucklaiid, in the autumn preceding the catastrophe
which is likely to attract so much more lively notice to these pbo;nomena, and must
therefore add so much of new interest to the views of which he is understood to be preparing an
account. Tliese valleys arc widely expanded e>;cavations in the great platform of BUckdowii ami
the East Devon hills, composed at their summit of cberty beds reposing on fox mould which in
the lower terraces of the slopes are based on marles, either of the lias or Pojcilitic group. The
fox mould throughout this district affords i-eiuariiahle facilities to the descrnctive agency of «'ater •
for the slightest rill, even the dminage by the side of a hedge, is found sufficient to wejir it duwii
into precipitous ravines, sometimes nearly 100 feet deep, locally culled goyles; and though all these
actions are slill in progress, it is evident that at periods more immediately succeeding the original
iormation of the valleys, they must have produced far more considerable effects i the general tendency
of all such causes being by the results oftheir first actions to diminish their future force, or
Iilace obstacles in iu way. Thus the land-springs which at first broke out along the junction of
a steep bed of .sand with the subjacent clay, and therefore rapidiv washed it awav, have now tg
ooze their way through subsided rocky masses, which both cheek the removal of the loose sand,
and form buttresses resting against and i)Bitly supporting the higher regions of the hill.
The writer of this memoir has found these views of iiis friend cast new light on some phienomena
in the oolitic valleys nearBunbury, which he has minutely described in the "Outlines of
the Geology of England and Wales," but for whicb at the time he was little able to account. Here
the cap of the hills is composed of the great ooUte, beneath which range the ferruginous sands of
the inferior oolite; but in the bottom of Uie valleys very consideiiible masses, often containing
two or three acres, of the upper white limestone of the great oolite are found thrown into a
highly mcliueil position. Early and extensive landslips noiv appear to the writer to afford a most
satisfactory explanation of these ciroumstanccs; and Mr. Marel.ison has stated that a careful
examination of the escarpment of the Cotteswold range in Gloucestershire affords many similar
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