CHAP. m. PROBABLE AGE OF UPRAISED STRATA. 55 



to the silting up of estuaries, and not to upheaval. Thus 

 Horsley insists on the difficulty of explaining the position of 

 certain Eoman stations, on the Solway, the Forth, and the 

 Clyde, without assuming that the sea has been excluded from 

 certain areas which it formerly occupied.* 



On a review of the whole evidence, geological and archaBo- 

 logical, afforded by the Scottish coast-line, we may conclude 

 that the last upheaval of twenty-five feet took place not only 

 since the first human population settled in the island ; but 

 long after metallic implements had come into use, and there 

 seems even a strong presumption in favour of the opinion 

 that the date of the elevation may have been subsequent to 

 the Eoman occupation. 



But the twenty-five feet rise is only the last stage of a long 

 antecedent process of elevation, for examples of recent marine 

 shells have been observed forty feet and upwards above the sea 

 in Ayrshire. At one of these localities, Mr. Smith of Jordan- 

 hill informs me that a rude ornament made of cannel coal 

 has been found on the coast in the parish of Dundonald, 

 lying fifty feet above the sea-level, on the surface of the 

 boulder-clay or till, and covered with gravel, containing 

 marine shells. If we suppose the upward movement to 

 have been uniform in central Scotland before and after the 

 Eoman era, and assume that as twenty-five feet indicate 

 seventeen centuries, so fifty feet imply a lapse of twice that 

 number, or 3400 years, we should then carry back the date 

 of the ornament in question to fifteen centuries before our era, 

 or to the days of Pharaoh, and the period usually assigned 

 to the exodus of the Israelites from Egypt. 



But all such estimates must be considered, in the present 

 state of science, as tentative and conjectural, since the rate 

 of movement of the land may not have been uniform, and its 



* Britannia, p. 157. I860. 



