ioo The Scottish Naturalist. 



crieffe Hill, must have been part of the same series. As the Mon- 

 creiffe Hill series also dip north-west, they must, of course, underlie 

 the Kinnoull Hill series, and must also have been laid down immedi- 

 ately prior to them. 



Kinnoull Hill, as it stands this day, is the result of three successive 

 processes, extending over a great interval of time. First, there was 

 the laying down of the sheets of lava, poured out in a molten state 

 from volcanic vents, whose activity gradually died out many ages 

 ago. These sheets were poured out over a level tract of country, 

 part of which, at least, was under water. The periods of activity 

 varied in duration and intensity. 



Sometimes sheet after sheet would be poured one on the top of the 

 other without intermission ; then a period of comparative quiescence 

 would intervene, and sufficient time would elapse for tolerably thick 

 deposits of sand and gravel to be laid quietly down on the bed of the 

 lagoon or sea. Again, the subterranean forces gathered head ; and a 

 vast shower of dust and stones was shot into the air by the bursting 

 open again of the choked up volcano or volcanoes. This loose 

 material was scattered all around, and fell on the beds of sand and 

 gravel, the dust forming the beds of tuff, and the coarser material 

 the beds of breccias that are now found underlying the Kinnoull Hill 

 lavas. After the loose material had been blown out, streams of lava 

 again poured forth, and obliterated the face of the land for miles ; and 

 continued their discharge till the beds had been filled up which now 

 form the cliffs of Kinnoull Hill. The total duration of volcanic 

 activity formed the first of the three stages in the history of Kinnoull 

 Hill. The geological date of the first stage could be determined 

 with certainty, for the sheets are interbedded with sandstones and 

 conglomerates of undoubted Old Red Sandstone age. The second 

 stage in the history was represented by the gradual upheaval of the 

 rocks from the horizontal position in which they were laid down to 

 the gently sloping position in which they are now found. When the 

 change took place, there are not any means of determining. The 

 third and final stage was that of denudation that is the stage re- 

 presented by the carving out of the valley which now separates 

 Kinnoull Hill from Moncrieffe Hill. When that process of denuda- 

 tion began, we are unable to say. It might have been, and probably 

 was, in progress long before the advent of the Great Ice Age ; or it 

 might have had its commencement in the grinding of the glaciers, 

 which have scored and polished the surface of the hill in many places. 

 One thing we do know, and that is that the process is going on still, 

 and that Nature's carving tools, frost, wind, rain, and stream, are as 

 busily at work to-day as ever they were. So much then for the history 

 of Kinnoull Hill, which may be summarised in the three words 

 deposition, upheaval, and denudation. 



