124 On Lilies of Ancient Sea-Levels. 



to the works of British geologists, and suggests, as indeed Mr 

 Phillips has done,* that the parallel roads of Glen Roy may, 

 by accurate measurement, be proved not to be parallel ; and 

 he then goes on to shew, that the lines of ancient sea-level of 

 comparatively modern periods, have undergone broad undula- 

 tions or great ascending and descending movements over ex- 

 tensive areas. 



Let us see how these views are strictly applicable to our 

 own country. The occurrence of ancient beaches containing 

 marine shells of existing species at different levels above the 

 sea, has long been observed by geologists in the British 

 Isles. Terraces of gravel have also been noted at various al- 

 titudes. In some instances they have been referred to the 

 formation of lakes, but in others they have been compared to 

 sea-shingle ; in many cases also they have been merged with 

 diluvial deposits, and latterly an endeavour has been made to 

 explain some of them by the action of glaciers which are sup- 

 posed to have barred up former lakes. It may be that we 

 should not endeavour to refer the whole of these phenomena 

 to one common origin ; though most persons muyt admit that 

 the mass of recent evidence proves the greater number of the 

 superficial deposits, to which allusion is now made, to have 

 been formed beneath the sea. Wherever, indeed, these ac- 

 cumulations are found to contain marine shells so imbedded in 

 the sand or gravel as to resemble sea-bottoms, and no doubt 

 can remain of their origin, the only question is, why do we 

 find these shells at such different altitudes ? why are the same 

 marine remains (appealing to British examples) placed at a 

 height of upwards of 1600 feet in North Wales, and a few feet 

 only above the sea in Devonshire and Cornwall, and at heights 

 varying from 200 to 400 in the central counties ? Most geo- 

 logists have been satisfied to reply (and I am myself of the 

 number), that in these evidences they had distinct proofs, not 

 that the sea had stood at an indefinite number of levels, there- 

 by making a most broken and irregular outline within the same 

 period (a supposition apparently absurd), but that the bottom 

 of the sea had undergone irregular oscillations, some points 



* See Penny Cyclopasdia, rarallcl roads. 



