PROCEEDINGS 



OF 



THE GEOLOGICAL SOCIETY OF LONDON. 



Vol. II. 1835. No. 40. 



February 25. — The Rev. William Thornton, of Brockhallj in North- 

 amptonshire ; Viscount Adare, F.R.S., of Adare, in the county of 

 Limerick ; and Thomas G. Parry, Esq., of Trinity College, Cam- 

 bridge 5 were elected Fellows of this Society. 



A paper was first read, " On the Volcanic Strata exposed by a 

 Section made on the site of the new Thermal Spring discovered near 

 the town of Torre del Annunziata, in the Bay of Naples ; with some 

 remarks on the Gases evolved by this and other Springs connected 

 with the Volcanos of Campania j" by Professor Daubeny, M.D., 

 F.G.S., &c. 



The discovery of a spring near Torre del Annunziata having oc- 

 casioned the removal of a considerable portion of a cliff, a clear sec- 

 tion has been exposed of the volcanic strata constituting that part of 

 the base of Vesuvius. The entire height of the cliff is 68 feet, and it 

 presents the following details : 



Vegetable mould, mixed with decomposed lava, 5 to 10 feet. 



Hard, compact, cellular lava, with occasionally considerable cavi- 

 ties, and scoriform at the bottom, 5 feet. 



In one of the cavities of this stratum, Dr. Daubeny states, on the 

 authority of Colonel Robinson, that a considerable quantity of car- 

 bonate of magnesia was found : and Dr. Daubeny also found in the 

 same lava a white coating, which appeared to contain a very large 

 proportion of it. The author further states that Colonel Robinson has 

 since informed him, that in endeavouring to find the origin of the 

 magnesia, he had excavated to the depth of 40 feet, two miles up 

 Vesuvius, in the direction of the spring, and had found large pieces 

 of pumice, the cavities of which were completely filled with carbonate 

 of magnesia. 



Under the bed of lava, the cliff is principally composed of strata of 

 rapilli and scoriae, of various shades of red, grey, and black, some- 

 times agglutinated by volcanic sand. In the upper portion the beds 

 are blended together, but in the lower they are, for the greater part, 

 tolerably distinct. In the midst of these strata is an irregular bed of 

 compact tuff, terminating abruptly at each extremity ; and at a lower 

 level are one or two other beds of similarly constituted tuff, but trace- 

 able only for a few feet. These beds of tuff. Dr. Daubeny is of opi- 

 nion, were formed on dry land, by rain or torrents, as eight or nine 

 feet lower in the cliff, is an admixture of vegetable mould containing 



VOL. II, Q 



