DILUVIAL OCCURRENCES. 79 
It removed the pebbles constituting beaches, and 
the beds ofrivers, and conveyed them even to eleva- 
ted spots ; besides the occurrence of these in caves 
nearly on a level with the general subjacent soil, 
they are discovered not infrequently in the smaller 
cavities towards the top of limerocks, and usually 
in the substance of a clay deposit. It removed 
loosened fragments of limestone, and scattered them 
in the vicinity of, and on the bed to which they be- 
longed, as seen plentifully in the vicinity of Plymouth, 
especially in the caves and fissures of the limestone, 
whither the substances whirled by the fluid would 
naturally tend ; itis not uncommon to find consoli- 
dated masses of bone, clay, pebbles, stalagmite, and ' 
irregular pieces of limestone in these hollows; and I 
lately saw a mass of firmly united rough fragments 
of limestone of several tons weight which had 
fallen from the brink of a lime quarry, where it 
had rested in a natural excavation of the rock. If 
acted on, and lossened the smaller and superficial 
fragments of slate and sandstone, carrying them 
with the general body of clay, in all the irregula- 
rities of its course. This mass of commixed clay, 
schist, sand, pebbles, and other uncertain frag- 
ments proceeded to fill up caves, fissures, and all 
the small crevices in the several kinds of strata ; 
some caves however are filled exclusively by sand, 
and some solely by clay, whilst the ordinary mixture 
is noticed in the spaces between certain parts of 
strata, as between trapp and slate, trapp and lime, &c. 
This mixed diluvial deposition is moreover seen in 
various places where natural hollows and pits had 
originally existed, and sometimes distinct stratifi- 
cation and alternation of the substances may be 
noticed. With respect also to the clay separately, 
it in some measure so acted on its harder portions 
as to roll it into balls like small boulders ; specimens 
of which occur in some of the caves of limestone. 
K 2 
