TRANSACTIONS OF SECTION C. 631 



presence of grits in the rilton lleds. Near Diilverton (Witlierwind) botli tlie 

 Cuculloea and Lingula Beds are distinguishable, but near Wiveliscombe the fossils 

 have been found in reverse positions, the Cucullsea zone being under the Lingula 

 slates. 



The rilton Beds are the most fossiliferous beds in the Devonian Series ; their junc- 

 tion with the Culm-Measures appears to be a palnsontological one near Dulverton, 

 but the nature of the evidence along the junction is, as a rule, very unsatisfactory. 

 Faults prevail near Morebath, but from Clayhanger eastward' the junction appears 

 to be perfectly conformable, following a feature line. 



9. The Bevono- Silurian Formation. By Professor E. Hull, LL.B., F.B.S. 



The beds which the author proposed to group under the above designation are 

 found at various parts of the British Isles, and to a slight extent on the Continent. 

 The formation is, however, eminently British, and occurs under various local 

 names, of which the following are the principal : — 



England and Wales. 



Devonshire. — ' The Foreland Grits and Slates,' lying below the Lower Devonian 

 beds C'Lynton Beds'). 



Welsh Borders.—'' The passage beds ' of Murchison, above the Upper Ludlow 

 Bone bed, and including the Downton Sandstone, and rocks of the Ridge of the 

 Trichrag. These beds form the connecting link between the Estuarine Devonian 

 beds of Hereford (generally, but erroneously, called the ' Old Fi,ed Sandstone,' 

 and the Upper Silurian Series). 



South-east of JSnr/land (Sab-Cretaceous district). — The author assumed, from 

 the borings at Ware, Turnford, and Tottenbam Court Road, described by 

 Mr. Etheridge, that the Devono-Silurian beds lie concealed between Turnford and 

 Tottenham Court Eoad on the south, and Hertford on the north. 



Ireland. 



Smith.— 'The Dingle Beds,' or 'GlengarlfF Grits and Slates,' with plants and 

 facoids, lying conformably on the Upper Silurian Beds, as seen in the coast of tbe 

 Dingle promontory, and overlain unconformably by either Old Red Sandstone, or 

 Lower Carboniferous Beds. They are from 10,000 to 12,000 feet in thickness. 



North.—' The Fintona Beds,' occupying large tracts of Londonderry, Monaghan, 

 and Tyrone, resting unconformably on the Lower Silurian beds of Pomeroy, and 

 overlain unconformably by the Old Red Sandstone, or Lower Carboniferous Beds ; 

 from 5,000 to 6,000 feet in thickness. 



Scotland. 



iSbzof/i.— Beds of tbe so-called 'Lower Old Red Sandstone' with fish and 

 crustaceans, included in Professor Geikie's ' Lake Orcadie, Lake Caledonia, and 

 Lake Cheviot,' underlying imconformably tlie Old Red Sandstone, and Lower 

 Calciferous Sandstone, and resting unconformably on Older Crystalline rocks. 

 Thickness in Caithness about 16,200 feet. 



The author considered that all these beds were representative of one another 

 in time; deposited under lacustrine or estuarine conditions ;_ and, as their name 

 indicated, forming a great group intermediate between the Silurian, on the one 

 hand, and the Devonian, on the other. He also submitted that their importance, as 

 indicated by their great development in Ireland and Scotland, entitled them to a 

 distinctive name, such as that proposed. 



10. On Evapm-atlon and Eccentricity as Co-factors in Glacial Periods. 

 By the Rev. E. Hill, M.A. 



As the temperature rises, the evaporation from water grows ; grows rapidly, and 

 Teith continually increasing rapidity. If at a steady temperature there be a steady 

 amount of evaporation, then the result of fluctuations m temperature will be to 



