638 



Mr. Clarke, in his survey, has noted as one division of the diluvium 

 of his district, a clay of a yellowish or bluish hue, containing rolled 

 pieces of chalk. This deposit is of great extent and thickness in East 

 Angha and the neighbouring parts ; and is worth notice, since this de- 

 posit is one main cause of the geological confusion and obscurity in 

 which that region is involved. In the neighbourhood of Cambridge 

 this diluvial deposit is called the broivn clay ; and I can state, from 

 my own experience, that the recognition of it as a separate bed at 

 once rendered the stratification clear, where it had long been unin- 

 telligible. 



Before quitting our stratified rocks, I may notice the commu- 

 nications respecting some of their fossils which we have received, 

 particularly that of Mr. Williamson on the fossil fishes of the Lan- 

 cashire coal field, and the establishment of the new genus Tropaeum, 

 separated from the Hamites of the green sand by Mr. Sowerby. 



In attempting to pursue a stratigraphical order, we are compelled 

 to reserve for a separate head the notice of unstratified rcfcks, since 

 their age and history are only known by the mode in which they in- 

 terrupt and disturb the rest of the series. We have not had many 

 communications respecting European rocks of this character ; but we 

 cannot but be struck by the subversion of ancient ideas which result 

 from the investigations of Messrs. Murchison and Sedgwick. They 

 have shown that the granite of Dartmoor, and consequently that of 

 Cornwall, formerly considered as one of the earliest monuments of 

 the primeval ages of the earth's history, is posterior to the deposit of 

 the culm measures. 



Advancing to newer phaenomena, we find the evidences of change 

 still unexhausted. We cannot but reflect how familiar those views 

 of the elevation and depression of portions of the earth's surface are 

 become, which were at first considered so strange and startling. This 

 is remarkably shown by the number of communications concerning 

 raised beaches which we have recently received. When we visit places 

 where these occur, and look at the winding shore, where the sea line 

 is faithfully followed or distantly imitated by terraces, sands and peb- 

 bles a little above it, we wonder that we should so long have been 

 blind to this kind of evidence. Such raised beaches have been de- 

 scribed during the past year, by Mr. Prestwich, as occurring in the 

 Murray Frith ; by Mr. Austin, in the valley of the Axe, the Exe, 



