﻿174 Geological Society : — 



exceeds 1000 feet iu diameter ; this cone was almost snow-white 

 from the deposit of sublimates. Many deaths were due to asphyxia, 

 but the collapse of roofs weighted with dust was a source of much 

 danger, as was the case at Pompeii in a.d. 79. The lava-streams 

 surrounded trees, many of which still stood in the hot lava with 

 their leaves and blossoms apparently uninjured. The sea-level 

 during the 7th and 8th of April was lowered 6 inches near Pozzuoli 

 and as much as 12 inches near Portici, and had not returned to its 

 previous level on April 18th. The maximum activity coincided 

 almost exactly with the full moon, and at the time the volcanoes oP 

 the Phlegraean Fields and of the Islands remained in their normal 

 condition. The author believes that this eruption of Vesuvius is 

 greater than any of those recorded in history, with two exceptions — 

 those of a.d. 79 and of 1631. 



2. ' The Ordovician Rocks of Western Caermarthenshire.' By 

 David Cledlyn Evans, P.G.S. 



The ground dealt with is practically identical with that examined 

 by the late Thomas Roberts, whose notes were published in 1893. 

 It extends from the River Cy wyn on the east to the Tave on the west, 

 and from the base of the Old Red Sandstone on the south to the top 

 of the Dicranograjrtus-Shales on the north. The area is, in the 

 main, a denuded anticlinal fold with an east-and-west axis, com- 

 plicated by minor folds, faulting, thrusting, and crushing. The 

 succession on the northern limb of the anticline is as follows : — 



Bala-Caradoc. 



Llandeilo, { V/cranozraptus-Beas 



I Asapmm-tyrannus .Beds. 



T f Didymoqraptus-Murchisoni Beds. 



LLANVIRN. 1 TV 7 j T, -J»3 T> 1 



[ Didymogra'ptus-bijidus Beds. 

 Arenig. Tetragrapttis-Beds. 



The succession on the southern limb is similar, but passes up into 

 higher beds, as shown below : — 



Lower Llandovery. 



{Slade Beds. 

 Bed hill Beds. 

 Sholeshook Beds. 

 Robeston-Wathen Limestone. 



Llandeilo, Llanvirn, and Arenig as above. 



The crushing and fracturing of the rocks has brought together 

 into a small area facies of rocks differing lithologically and in 

 faunas, the difference being well shown in corresponding beds on 



