PERIOD OF INVASION BY THE SEA. 111 
furnished at its entrance with an imperfect bar, or 
bridge of rocks formerly perhaps protecting this 
area of country from the sea. Had the ocean 
tenanted this basin a greater number of years, no 
doubt this barrier would ere this time ne dis- 
appeared. 
It might be conceived, that since tite, Bovey 
Heathfield formations consist of dicotyledonous 
trees, &c. in an imperfectly mineralized state, and 
associated with clay, gravel, &c. they were con- 
temporaneous with the submerged forests of the 
coast, which are moreover, likewise accompanied 
by clay. There are however no indications of a 
beach so far removed from the present sea-mark as 
is the site above mentioned ; the elevations of the 
sea subsequently to the last great geological catas- 
trophe do not seem to have devastated the land so 
extensively as to have reached that far. Had the 
ocean risen to such an extent, and continued long © 
enough in that position to have partially mineralized 
vegetation, unequivocal proofs would have been 
bequeathed to us in regard of the exact line of its 
innovation. Besides which, the relative positions 
of the trees and clay are in the two cases opposite ;— 
in the one, the clay was carried over the country 
_ by the powerful undulations of the devastating and 
outspread element, and finally deposited wpon the 
vegetation which had been sacrificed by its ravages; 
in the other, the sudden and limited rise of the sea 
overwhelmed the forests of the coast, whose found- 
ation consisted of clay the proceeds of the very 
flood which had preceded. Could it be shewn, 
that besides the mineral state of the trees of the 
Bovey basin, specific differences exist between 
them and those submerged on the coast, the ques- 
tion would be settled beyond doubt. 
What that period was in which the sea rose 
upon the land (or land sunk into the sea) to such 
