115 



Uranus on tlie Hypothesis of Disturbances cuused by a more 



Distant Planet. By J. C. Adams, Esq. M.A. By the Author. 

 Scheikundige Onderzoekingen gedaan in het Laboratoriuni der 



Utrechtsche Iloogeschool. Deel 4dc-. Stuk !«*«• — By the 



Editors. 

 Guide to the Geology of Scotland. By James Nicol, Esq. — By 



the Author. 

 Account of Iceland, Greenland, and the Faroe Islands. By the 



same. — By the Author. 

 Specimen of Metamorphic Limestone, dislocated by the vicinity of 



Trap-Rocks, near North Berwick. — By Sir G. S. Mackenzie, 



Bart. 



Monday, 15th February 1847. 

 Dr CHRISTISO.N, Vice-President, in the Chair. 

 The following Communications were read : — 



1. A Speculation, connecting the origin of Trap-TuflP, the 

 cause of Earthquakes, and of Partial Changes of the 

 Bed of the Ocean. Part II. By Sir G. S. Mackenzie, Bart. 



The author, having observed in Iceland some remarkable intermix- 

 tures of lava with volcanic tufF; and, more recently, on the coast of 

 East Lothian, a somewhat similar intermixture of masses of green- 

 stone in trap-tuff, conceived the idea that cavities existed underneath 

 the crust of the earth, or deeply seated within it, containing water 

 exposed to heat, and the agitation of which, occasioned by the produc- 

 tion of steam, had reduced the materials of trap-tuft' to the state in 

 which we find them, which had been afterwards erupted at the bot- 

 tom of the sea, or forced between the beds of superincumbent rocks. 

 Some time afterwards, on reading the researches of Mr Hopkins in 

 Physical Geology, he was gratified to find that profound philosopher 

 advocating the existence of vast cavities containing lava, and connected 

 with volcanic vents at a depth such as would admit of steam-power 

 throwing the lava to the surface. It did not now appear difficult to 

 imagine similar cavities containing heated water, and the materials 

 of trap-tuff; and he therefore extended the hypothesis of Mr Hop- 

 kins so as to account for its origin, and for masses of trap occurring 

 in it, the form of which seemed to indicate that they had been forced 

 into the tuff at the time of its eruption, from some neighbouring 

 cavity containing melted matter. 



