154 Proceedings of the Royal Physical Society. 



able avenues of advance. In other words, I believe the 

 pressure was strong enough to force a few over the moun- 

 tain passes between the rivers Esk and Muick, also between 

 Glen Muick and Glen Tanar, while the wave rolled onward 

 into Kincardine ; but I doubt if the pressure was sufficient to 

 make them encounter the longer journeys via Glen Tilt and 

 Glenshee. The comparative absence of wood in the northern 

 glens of Forfar at an early date caused the strongest wave to 

 set more to the eastward. 



At the same time, it is right to mention one of the most 

 striking instances of the species surmounting difficulties 

 with which I am acquainted. The Eev. W. Gordon relates 

 as follows : " Some years ago, probably ten or twelve — say 

 1867 — Lord Sandys, then the guest of Lord Holmesdale at 

 Old Mar Lodge, was out shooting, accompanied by his Lord- 

 ship's head gamekeeper and two young men who are now 

 gamekeepers in the district. While they were crossing one 

 of the highest peaks of Ben-y-Bhrotan, they were surprised 

 to come upon a squirrel. Being unable to catch it, they 

 unleashed two staghounds, one of which speedily arrested 

 the squirrel's progress by putting his paw gently upon it. 

 One of the men was severely bitten by it." This squirrel 

 was taken to Mar Lodge, but a terrier scraping open the 

 box, the squirrel escaped into the woods. The nearest tree 

 to the peak of Ben-y-Bhrotan, on which it was found, was 

 at least nine miles distant — viz., in Glen Derry — and the 

 height of Ben-y-Bhrotan is 3825 feet {vide remarks under 

 Strathdon, next page). 



Mr James A. Haldane's keeper at Keith Lodge, Banff, who 

 was born on Crathes estate on Deeside, killed a squirrel there 

 when he was underkeeper about twenty years ago — say 1859. 

 He had never seen squirrels before, and shot one for a weasel, 

 for which he was reprimanded, as only two (both of which he 

 saw) were known on the place : but before he left, about three 

 years later, there was any amount to be seen. Thus it would 

 appear that an almost simultaneous advance was made into 

 Aberdeenshire at various points along the range of hills be- 

 tween Aberdeenshire and Forfar, and through Kincardine- 

 shire. The natural advance from these points would probably 



