862 REPORT — 1898. 



The following Papers and Reports were read : — 



1. Rotes on the Geology of the Bristol District. 

 By Professor C. Lloyd Morgan, F.G.S. 



(a) The chief features of the Silurian district of Tortworth were^ briefly de- 

 scribed. Attention was drawn to the probably contemporaneous Upper Llan- 

 dovery volcanic action. One or two new facts, as given in the ' Guide ' to the 

 excursion to this locality, were alluded to. (d) The division of the Carboniferous 

 Limestone (between the Upper and Lower Limestone Shales) into an Upper and 

 Lower Series with a band of Oolite, the Gully Oolite, between them, was illus- 

 trated by typical sections in the Bristol district, (c) An interbedded volcanic 

 series near the top of the Lower Limestone at Woodspring, near AVeston, was 

 illustrated by a map and photographs from microscopic sections. (<f) Slides were 

 shown illustrating the unconformabilities of the district, and a sketch map of the 

 islands in late Triassic times was briefly described, (e) An attempt was made 

 to illustrate, by means of a diagram based on careful observations, the amount of 

 superficial contraction due to post-Carboniferous lateral pressure. 



2. The Building of Clifton Rocks. By E. B. Wethered, F.G.S. 



In tills paper the author confines his remarks chiefly to the microscopic life 

 which he has discovered in the Carboniferous Limestone rocks at Clifton. He 

 contends that microscopic calcareous organisms have been the chief contributors to 

 the vast deposits in the Carboniferous sea, now represented by the cliffs on either 

 side of the gorge of the Avon at Clifton. 



Broadly speaking, there were three stages in the formation of this limestone. 

 These were regulated by physical conditions, and favoured the existence of certain 

 forms of life. The fossil remains now denote the stages. They are as follows : — 



Approximate Thickness 

 Stage 1. Lower Limestones (including the Lower 



Limestone shales 500 feet, and Black Rock 



series 470 feet 990 feet 



Stage 2. Middle Limestone 1,620 „ 



Stage 3. Upper Limestone 100 „ 



The close of the Old Red Sandstone Period is marked by variegated sandstones 

 and shales. These beds pass into limestones and shales, and these again are followed 

 by massive limestones locally known as the Black Rock ; the whole representing 

 the Lower Limestones, or Stage 1. 



During this stage encrinites were so numerous in the waters that the ossicles 

 of these creatures are a distinguishing feature of the limestones. Vast numbers of 

 ostracoda at times lived, and some beds of the limestone are chiefly accumulations 

 of the remain.^ of these small crustaceans. Monticulipora corals and polyzoa were 

 numerous in the waters, and also moUusca. 



Another interesting feature, not before noticed in the Lower Limestones, is the 

 mass of incrusting organisms. These organisms formed a crust around the 

 fra^mental remains of other organisms which collected on the sea floor, and to 

 such an extent did this process go on that the incrusting organisms contribute 

 considerably to the building up of some beds of limestone. Whether these crusts 

 are to be attributed to animal or vegetable growth is a matter of doubt. 



The crinoidal life reached a climax during the time that the Black Rock 

 Limestone was in process of formation. Indeed, this rock is, in the main, a vast 

 accumulation of the ossicles of these creatures, associated with shells of mollusca, 

 fish I'emains, &c. 



The Black Rock series terminate in dolomitised limestone, and on this rest the 

 ' Gull V Oolites.' 



The Lower Limestones terminate at these oolites, in which occur, though 

 sparingly, foraminifera and the minute spherical object calcisphsera. This latter 



