ON EARTHQUAKES IN SCOTLAND. 197 



the present channel of the river as the streets of the lower part of the 

 village, skeletons of whales have been found. The upper or northern part 

 of the village stands upon a high terrace of Old Eed Sandstone, traversed by 

 whin dykes, alongside one of which its famous Spa is discharged. The front 

 of this terrace runs east and west, and forms the former sea-margin, hewed 

 out by the waves of the old estuary, against which the alluvium rests to an 

 unknown depth. The town of Stirhng stands upon the south side of the 

 Forth valley, partly on alluvium and partly on a trap ridge erupted through 

 Old Eed Sandstone. Eastwards from Bridge of Allan by Blair Logic and 

 Dollar, the Ochill HiUs, of which the terrace at Bridge of Allan is the first 

 ridge or step, are composed of the same Old Sandstone, broken through and 

 overlain by a vast body of trap rocks, clay-stones, and porphyries, and pre- 

 sent a waU-like front to the Forth valley on the south. They completely cut 

 off the Coal-measures, tilting up the strata at a high angle, altering the coal 

 to the state of coke, shale to Lydian stone, and sandstone to quartzite. 

 Dunblane, Greenloaning and Ardoch, and the wild moorlands N.W. to 

 Crieff' are composed of Old Red Sandstone pervaded by traps ; and Crieff and 

 Comrie are close upon the junction of the sandstone and old slates of the 

 mountain-region. Glen Lednock and a large area E. of it towards Crieff are 

 occupied by an eruptive granite which sends veins into the slate, and whose 

 outer edge approaches close to the boundary of the slate and sandstone. 

 Whatever the cause of this earthquake may have been — masses of rock fall- 

 ing from the roof of a vast cavern, or a sudden impact of high-pressure 

 steam emanating from the nether depths — all the strata were affected by it, 

 and sent the awful tremor, yet with varying intensity, alike along beds of 

 rock and alluvial strata. 



The particulars in regard to the earthquake in the south of Scotland have 

 been kindly supplied by Dr. Grierson and Mr. Henrison, Thornhill, Dum- 

 fries, and Mr. J. Shaw, Tyrnon parish. The earthquake took place on the 

 16th of April, 1873, at 9^ 55"" p.m. A smart concussion, producing a con- 

 siderable sound, noise, or crash, as it is variously described, and causing a 

 perceptible movement in fixed objects, and an oscillation of those suspended, 

 was experienced in the parishes of Tyrnon, Glen Cairn, Keir, Penpont, Mor- 

 ton, Closeburn, and Balmaclelland. Doors and windows were made to 

 rattle ; there was a sensible vibration of walls and floors in many places; and 

 objects near one another (as glasses and china on shelves) wore knocked 

 together. In some cases alarm was shown by the lower animals. But the 

 wave or undulation was not observed with any thing like precision, except 

 in one case, in which a floor was distinctly seen to have such a movement. 

 The late hour, however, was unfavourable for observation on the part of 

 many persons. One only of the observers whose accounts have been fur- 

 nished to me had any previous experience of earthquakes. This gentleman 

 had resided for some time in the East. Another witness, in every way com- 

 petent, experienced a repetition of the shock at Thornhill at S** 46" a.m. on 

 the following morning ; but no information regarding this second shock has 

 reached me from any other part of the district. 



