424 ON A SUBMARINE FOREST IN THE FRITH OF TAY. 



eighteen feet in thickness, would be permitted to remain, un- 

 til washed away by the slow force of percolating fresh water, 

 or that a continuous bed of peat, of nearly an acre in extent 

 would be spared from destruction, and suffered to settle peace- 

 fully, in the Bay of Skaill, so as to be covered at flood-tide 

 with fifteen feet of water. 



If we have no reason to doubt that this Tay-bed was trans- 

 ported to its present situation, in what manner has it reached 

 its present level ? Two solutions of this curious question have 

 been offered, as connected with similar occurrences, by emi- 

 nent individuals, Dr Borlase, Dr J. Courea de Serra, and 

 Professor Playfair. 



Dr Borlase, who, in 1757, observed a submarine forest at 

 Mount's Bay, Cornwall, covered at full tide with twelve feet 

 of water, considered the depression of the bed, which support- 

 ed the trees, and still contained their roots in situ, as having 

 arisen from subsidence of the ground, produced by earth- 

 quakes, or, to state it in his own words, " that there has been 

 " a subsidence of the sea-shore hereabouts, is hinted in my 

 " letter to you, p. 92 ; and the different levels and tendencies 

 " which we observed in the positions of the trees we found 

 " afford us some material inferences as to the degree and ine- 

 " qualities of such subsidences in general ; as the age in which 

 " this subsidence happened (near 1000 years since at least) 

 " may convince us, that when earthquakes happen, it is well 

 " for the country that they are attended with subsidences • 

 " for then the ground settles, and the inflammable matter 

 " which occasioned the earthquake, has no longer room to 

 " spread, unite and recruit its forces, so as to create frequent 

 " and subsequent earthquakes ; whereas, where there are 

 " earthquakes without proportional, subsidences, there the ca- 

 " verns and ducts underground remaining open and unchoak- 



" ed, 



