40 REV. G. R. HALL ON 



through the mountain passes, as the blockage by glaciers or ice- 

 bergs was removed from time to time. This theory for the for- 

 mation of the Glen Roy terraces, and of some others on a much 

 smaller scale, seems now to be generally followed. And, indeed, 

 there are in this district of Western Northumberland some tra- 

 ces of glacial action, which might, to a certain extent, account 

 for similar phenomena, and influence us so far as to assign, per- 

 haps, a portion of the terraced slopes of North Tynedale to that 

 efficient cause. If we go in imagination back to the strange 

 epoch of the "Drift formation," as it is usually termed, when 

 an Arctic climate rested on these islands, we see only a few 

 summits of our present mountains and hills appearing above the 

 great sea, like islets, beneath which lie submerged the pleasant 

 valleys and fertile plains that we now behold. This valley and 

 its tributary vales would then form a series of lakes — a chain of 

 "loughs," of various degrees of depth, of which there are a few 

 minor representatives along the line of the Roman Wall still re- 

 maining in what we call our " Northumbrian lakes." Above the 

 present junction of the North Tyne and Rede there would be, at 

 that remote period, such a lake, until the softer strata between 

 the Garrett Holt Hill and the Buteland ridge were worn through 

 by the eroding pressure from above. Another lake must have 

 engulphed the now open space of the valley between this barrier 

 and the hard free-stone strata which crossed from the Chipchase 

 Park House quarry to the southern bank of Wark Burn, A still 

 more extensive tract must have lain under water (perhaps divi- 

 ded off for a time into two lakes by the great basaltic ridge crop- 

 ping out at Gunnerton) between the barrier at Chipchase and 

 another high free-stone ridge, once closing up the narrow pass 

 between the Vfall and Warden Hills. From many a vantage- 

 ground, such as the Gunnerton Crags, the ancient outline of this 

 inland lake is very marked, with the hilly slopes so perfectly en- 

 circling it, that it would not be possible for the spectator, if a 

 stranger, to tell where the long-imprisoned waters had at length 

 burst their primeval barrier, and escaped through the estuary of 

 the Tyne valley into the great glacial sea. We are not left merely 

 to our imaginations in picturing this scene. Undoubtedly there 



