on the Cuast ufTiree, S^c. 133 



love for explanation, be allowed to suppose rivers, and lakes, 

 and detritus, the filling up of a basin, the lake on a level with 

 the sea, the formation of land in its place, the growth of trees, 

 the destruction of the seaward barrier, the drainage, the subsi- 

 dence, and the consequent overflo\ving, even perhaps in such a 

 place as Tiree, where none of these at present exist ; but when 

 the facts are so numerous, and found under such a variety of 

 circumstances, sometimes in friths, sometiraes in bays into which 

 no stream now flows, and always where other symptoms of lakes 

 are deficient ; when they are so frequent, that, by the above sup- 

 position, we must consider a variety of particular and fortui- 

 tous causes in general operation, before we can admit its truth, 

 it appears to me that some strong foundation should be found 

 in fact before the theory can be deemed legitimate. The exisU 

 ence of lacustrine silt under the submarine moss, may be a foun- 

 dation of this nature. But might it not be requisite to show, 

 that it is always found under submarine forests ; that it is not 

 to be found except in situations where lakes have undoubtedly 

 existed ; that its characters are universal and decided, and that 

 its existence and properties are incompatible with any other sup- 

 position or illustration, before it can justify us in making any 

 decided statement ? I am not aware that this has been done or 

 attempted. 



Other explanations have been given. The effects of earth- 

 quakes in destroying whole districts, and otherwise changing the 

 relative levels of different portions of the earth, have been but 

 too frequently marked. Accordingly, Dr Borlase, in his re- 

 marks upon the present state of the Scilly Islands, and the 

 appearance at Mount's Bay*, has attributed these to the agency 

 of central heat excavating, agitating, and finally depressing this 

 portion of country. Correa de Serra is of the same opinion •}^. 

 Calculating upon the force with which the level of soft grounds 

 is borne down by the operation of the ordinary laws of gravity, 

 he considered that this natural force of subsidence, called into 

 sudden and violent action by the instrumentality of an earth- 

 quake, was the most easy mode of accounting for the appear- 

 ances at Lincoln. Wherever earthquakes have exerted a local 



• Phil. Trans. 1787. t Ibid. 1789. 



