1862.] HULL CARBONIFEKOUS STRATA. 127 



On the 16th heavy rains fell, the weather having been quite 

 clear and tranquil up to that time. On a second visit made on the 

 23rd of December, I ascertained the number of openings, marked by 

 minor cones with funnel-shaped craters, that had been formed on 

 the flank of the mountain were about twelve — ranged close together 

 on a line from E.N.E. to W.S.W. at the distance of about 600 metres 

 S.S.E. from the old lateral crater whence the lava-stream of 1794 

 proceeded which had poured down on Torre del Greco. Thus it 

 appears that a fissure had on this occasion been formed in the side 

 of the mountain, either on the prolongation of that of 1794, or 

 parallel and close to it. The lavas produced by the two eruptions are 

 also almost identical in mineral character, being very poor in leucite, 

 but rich in augite crystals. 



On returning to Torre del Greco, I was surprised to find the prin- 

 cipal fountains of the town overflowing with an excessive supply of 

 water, as in general during eruptions the springs are rather apt to 

 fail. Bubbles of carbonic acid gas were rising abundantly from the 

 water. Many of the cracks which had been formed by the earth- 

 quakes in the pavement of the streets of the town were seen, it is 

 said, to emit small flames (of carburetted hydrogen ?). It is certain 

 that the shore beneath Torre del Greco was permanently elevated by 

 above a metre — a long white line composed of mollusks and zoophytes 

 attached to the rock, which only live under water, being now gene- 

 rally raised that much above the sea-level, through a space of at 

 least two kilometres. 



The cone of Vesuvius continued to smoke at intervals for several 

 days. On the 23rd of December ashes fell abundantly in the streets 

 of Naples — a circumstance that has not occurred since 1822. 



3. On Iso-DTA METRIC LiNES, as means of representing the Distribution 

 of Sedimentary Clay and Sandy Strata, as distinguished from 

 Calcareous Strata, with special reference to the Carboniferous 

 EocKs of Britain. By Edward Hull, B.A., F.G.S., of the Geo- 

 logical Survey of Great Britain. 



[Plate VII.] 

 Contents. 



I. Introduction. — Comparison of Argillaceo-arenaceous with Calcareous Sedi- 



ments, as to their range in Modern and Ancient Seas. 

 Recent — Caribbean Sea, &c. 

 Past — Oolites of Oxfordshire and Yorkshire. 



Permian Strata of England. 



Lower Carboniferous Strata of Belgium and Westphalia. 



Nature of Calcareous Deposits. 



Contemporaneity of the Deposits and Oscillation of the Land. 

 Threefold arrangement of Groups with a calcareous centre. 

 Iso-diametric aspect of Strata. 



II. Carboniferous Land-sui'face of Central England — Existence of an old E. and 



W. Barrier. 



