36 



directions from a common centre, — the Pentland Hills, forming the 

 southern boundary, the rocky coast of Fife at Burntisland the north- 

 ern, and Salisbury Craigs and Corstorphine Hill the eastern and 

 western limits. 



The paper then proceeds to describe the appearances presented by a 

 late section of the southern face of the Castle Hill, where several of the 

 phenomena referred to above are very well illustrated. The great mass 

 of the Castle Hill rock is a dark compact greenstone. Towards the 

 south-west point, altered rocks are seen resting on the trap in a highly 

 inclined position ; and within the Castle wall, fragments of sandstone 

 are imbedded in the greenstone, shelving that the latter must have 

 burst in a state of fusion through the strata of the former. But at 

 the south-east point of the rock, beyond the walls, the section lately 

 made in cutting the new south-west road has displayed appearances, 

 which, in the author's opinion, supply strong evidence that, subse- 

 quent to such eruption, the secondary and trap-rocks had been up- 

 lifted together by a common cause, probably acting on a great extent 

 of the face of the country. This section shews five or six beds of 

 sandstone, with alternate layers of slate-clay or marl. Signs of 

 great confusion are found in these strata, more especially as they 

 approach the point of junction with the trap rock, — their eastern 

 extremity being thrown upwards, while their western portion is cast 

 down, so as to lie unconformably on the upturned strata; and near 

 the point of junction with the greenstone, the ends of the strata of 

 sandstone and slate-clay are shattered, and have actually fallen over, 

 so as to come obliquely in contact with the tabular masses of the 

 greenstone. Yet it is remarkable, that the sandstone and shale pre- 

 sent no appearance of semi-fusion or intermixture, where they are 

 in contact with the greenstone ; nor does the greenstone here pre- 

 sent any imbedded masses of the secondary rocks, nor send out any 

 veins among their adjacent strata. At the time, therefore, when 

 the dislocation of the sandstone strata occurred at the point of junc- 

 tion with the greenstone, the latter could not have been in a state of 

 fusion; and the only rational explanation which occurs is, that both 

 rocks were raised, in a solid state, by some common cause, above the 

 level of the waters under which they were originally formed ; and 

 that the fault or dislocation in the sandstone strata was produced by 

 some subsidiary disturbing power acting at the same period. 



2. Eesearches on the Vibrations of Pendulums in Fluid 

 Mediums. By George Green, Esq. Communicated by 

 Sir G. Ffrench Bromhead, Bart. 



The author proposes in this paper to resolve a particular case of 



