104 Mr D. Milne on Earthqt(akc->'<liockf:fcll in G reat Britain, 



lation had ])assed. Yet it must be observed, that they were 

 quite distinct and separate from the first undulation. In 

 order that you may obtain the inclination or slope of the wave, 

 which was convex, I have measured the height of the clock, 

 which is exactly 6 feet 11 inches. You may take the distance 

 of the clock off the perpendicular, at Si- inches. The slope of 

 the table at which I was writing was, as nearly as I can de- 

 termine after trial, about 7° from the horizontal. I am quite 

 certain that the two tremulous motions were exactly across 

 the path of the first undulatory shock ; the former were con- 

 cave, the latter was convex ; the former had not above one- 

 fourth of the power of the latter, though, taken together, they 

 lasted rather longer." 



In another letter, Mr Jeffi'ey corrected the estimate he had 

 made of the degree to which the table was inclined, and limited 

 it to 4i degrees. He also added, that he has " a sensible 

 recollection of hearing the pendulum strike the sides of the 

 clock, — but how often I cannot say." As to the duration of 

 the undulation and the lateral vibrations respectively, Mr Jef- 

 frey observes, — " The first undulation took 1|'' to pass, — then 

 say that |" elapsed between the first undulation and the side 

 movements. This leaves about 3" for them, which is perhaps 

 rather above than below the time which they occupied." 



Two things are remarkable in these accounts fi'om Throsk, 

 especially when contrasted with the eft'ects observed in places 

 not remote from it. The first is the absence of all noise, not- 

 withstanding the violence of the heave. The second is the 

 extent to which the clock and table Avere seen by Mr Jeft'ray 

 to deviate from the perpendicular. Judging by the eye, Mr 

 Jeffrey thought the table sloped to the horizon at an angle of 

 about 4^.° On the other hand, if the top of the clock was 

 5i- inches from the perpendicular, it must have deviated to the 

 extent of only 3° 47'. 



In Stirling, as the Messrs Drummond wrote, " the shock 

 was most perceptible around the base of the hill, where a com- 

 bination of the heave and tremor was felt. In the upper parts 

 of the town situated on rock, there was merely a tremor or vi- 

 bration." The rock here referred to is a mass of greenstone, 

 on which the castle and the older part of the town is built. 



