146 Scientific Intelligence. [Aug. 



tain, owing to the breaking out of a more considerable current on the 

 opposite side of the mountain. 



This latter took the direction of the township of Ottayano, sweep- 

 ing away in its course several small villages, and about 180 houses. 



The lava when visited by Dr. Daubeny even so late as the end of 

 December, or four months after the time of its emission, still 

 possessed a high temperature, and was exhaling much steam, free 

 muriatic acid, and sal-ammoniac ; which latter appears from former 

 observations to be a common product of volcanic action. 



It remains to be explained, first, how this and other volatile 

 matter can remain for so long a time pent up within the substance of 

 the heated mass ; secondly, how this salt was in the first instance 

 generated in the bowels of the earth. 



The first question may perhaps be answered by supposing the 

 body, whilst within the mountain, to have been entangled in the 

 lava, and there to have been confined by the enormous pressure of 

 the superincumbent mass ; so that when the eruption took place, 

 the volatile matter did not at once find the means of escape, but 

 continued in part locked up within the pores of the viscous mass. 



The second question requires for its answer a consideration of the 

 causes of volcanic action in general. 



The president brought forward some facts and authorities bearing 

 on the question whether Pompeii was destroyed by the eruption of 

 A. D. 79. 



That Herculaneum and Pompeii suffered from an earthquake in 

 A. D. 62 or 63, appears from Tacitus Ann. XV. 22. and Seneca 

 Nat. Quaest. VI. 1. 



Pliny in mentioning the eruption says nothing of these cities. 



Tacitus speaks of some cities being destroyed during the reign of 

 Titus A. D. 79-81. s y & B 



Dio Cassius (in A. D. 229) expressly says, that Herculaneum and 

 Pompeii were destroyed by an eruption in the reign of Titus 

 (LXVI. 23.) 



From Statins (A. D 95) it would seem they were not wholltf 

 destroyed. Florus (A. D. 116—120) mentions them as still existing. 



M. Aurelius, however, mentions them as entirely destroyed before 

 A. D. 161 (IV. 18) ; as alsd TertuUian (Apol. 40) in A. D. 200. 



Some further discussion took place: and Mr. Twiss mentioned, 

 as a well ascertained fact, that Stromboli is always active when the 

 Sirocco blows, but at no other time. 



Mat/ I5th. — A paper was read by the Rev. R. Hussey of Ch. 

 Ch. on the standard and value of some ancient coins. 



After some account of the experiments hitherto made for finding 

 the standard of the silver of the ancient currencies, the results of 

 assays of some coins were reported, and the value of them calculated. 

 From the analysis of a quinarius of Rome in the time of the consul- 

 ship, the value of the denarius of 60 grains weight, compared with 

 our silver currency, was computed to be nearly Sf^/. The Attic 

 drachma of 66^ grains weight was computed, from the assay of 

 three drachmffi of different ages, to have been from 9Jf/. to 9^.4 in 



