316 Dr. Mac Culloch on the Geology of Glen Tilt* 



I have reserved for a separate description some interesting 

 circumstances relating to Glen Tilt, because they are extraneous to 

 the general appearances, which required to be considered in one 

 collective point of view, and because they would have interrupted 

 the continuity of the narrative. The first of these is a deposition 

 of calcareous matter, which was pointed out to me by the Duke of 

 Atholl, to whose unwearied kindness and friendship I am no less 

 indebted for the facility which I experienced in examining this 

 district, than the science of geology is for this very interesting fact. 

 On the brow of the hill above Gow's bridge a large bed of shell marie 

 is to be seen. It is found on the left side of the river commencing 

 under a face of limestone and extending for about 250 feet or 

 more down the hill. It is between 80 and 90 feet wide, and its 

 depth seems to vary from one foot to six or more. This 

 appearance is unexpected but it is not solitary, as another similar 

 instance occurs at the foot of the limestone ridge d!t the south of 

 Ben Gloe, as well as on the hill of Tulloch formerly mentioned, 

 but in neither of these cases so well marked or so extensive as the 

 present. 



The formation of shell marie in the peat mosses of Scotland is 

 I believe well known to the Society, as it has long been to the 

 agriculturists of Scotland. These deposits are by no means 

 uncommon, whether in the larger tracts of peat, or in the smaller ones 

 which are found occupying insulated patches on those hollows in 

 the mountains which are favourable to the growth of this substance. 

 They are found forming beds, generally of no great thickness, but 

 varying from an inch or two to as many feet, and lying under the 



