654 FOURTH REPORT — 1834. 



taining fossil shells of the same species which now characterize 

 the brackish waters of that sea. These occur at various eleva- 

 tions of from 1 to 100 feet, and sometimes reach 50 miles inland. 

 The shells are partly marine and partly fluviatile : the marine 

 species are identical with those now Uving in the ocean, but are 

 dwarfish in size, and never attain the average dimensions of 

 those which live in waters sufficiently salt to enable them to 

 reach their full development. Mr. Lyell concluded by declar- 

 ing his belief that certain parts of Sweden are undergoing a gra- 

 dual rise to the amount of two or three feet in a century, while 

 other parts visited by him, further to the south, appear to ex- 

 perience no movement. 



On Marine Shells of recent Species, at considerable elevations, 

 near Presto)i. By W. Gilbertson. 



The situation of these fossils is in the county of Lancaster, 

 betwixt the Lune and the Mersey : the greatest elevation at 

 which they have yet been found is 350 feet above the sea, in the 

 excavations made by the Preston Water Company at the foot of 

 Longridge Fell. 



The shells are interesting, as being of the same species as 

 those now found on our shores ; and showing, therefore, that 

 this elevation has taken place since the creation of existing 

 species : and the stations and roads of the Romans being upon 

 this deposit, prove that there has been no change in the form 

 of existing species during the period that has elapsed since they 

 occupied this country. 



Notices in reply to a Question proposed by the Geological 

 Committee at Cambridge, as to the Relations of Mineral 

 Veins and the Non-metalliferous Joints in Rocks. By John 

 Phillips, F.R.S. G.S., Professor of Geology in King's Col- 

 lege, London. 



The author states that his attention was first drawn to the 

 special investigation of the direction and other characters of the 

 joints of rocks, during an examination of the upper slate system 

 of Westmoreland and Yorkshire in 1823*, and again excited by 

 observations on the magnesian limestone of the North of En- 

 gland in 1828t. Since that period he has at different times ga- 

 thered additional facts on the subject by investigations among 



* Transactions of the Geological Society, vol. iii. p. 1. 

 t Phil. Mag. and Annals, vol. iv. (1828.) p. 401. 



