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Anali/sis of a singular Substance found among the Products of 

 the Eruption of Vesuvius in the winter 1830. By Wil- 

 liam Gregory, M. D. F. R. S. E. Lecturer on Chemistry, 

 &c. Communicated by the Author. 



X HIS substance was put into my hands along with some other 

 volcanic productions, by Mr R. Allan, accompanied with the 

 following account of the situation in which it was found. 



" During the month of November 1830, Vesuvius was in a state 

 -of considerable activity, throwing up from the small cone which 

 occupied the centre of its crater constant showers of scoria and 

 stones, to the height sometimes of 500 or 600 feet. These ejec- 

 tions gradually increased till the 3d of December, when they 

 became so violent as for ten days to preclude the possibility of 

 ascending the mountain. Much liquid lava from time to time 

 flowed from the cone upon the surface of the surrounding cra- 

 zier, causing it, within the short period of six weeks, to be filled 

 up nearly 200 feet, and raising the level of the crater to within 

 50 feet of its edge. In the middle of December, the volcano 

 became suddenly more quiescent, and by the end of that month 

 it was possible not only to descend into the crater, but even to 

 mount the cone in its centre. During the month of January, 

 its volcanic activity gradually subsided, and towards the end of 

 that month presented no farther appearance of action, than emit- 

 ting volumes of smoke, and acidulous fumes, from an infinity of 

 vents within the crater. Several interesting sublimations were 

 at the same time deposited on the rugged and broken surface of 

 the lava, among which the sulphuric and muriatic salts seemed 

 greatly to prevail. The fumes were in many places intolerable, 

 and the pungency of the chlorine excessive." 



" On the surface of a partial hollow, consisting of black volca- 

 nic lapillae, occupying a space of perhaps eight or ten yards in dia- 

 meter, and at the distance of 100 or more from the mouth of 

 the cone, appeared an exceedingly beautiful, bright orange- 

 coloured salt. Being merely superficial, it was collected with 

 some difficulty ; the muriatic fumes arising from it were most 

 suffocating ; and the ground around it was too warm to admit 

 of keeping the feet in one position even for a few seconds. In 



