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Vesuvius and Meteorological Phenomena. [Mar. 18, 



March 18, 1886. 



Professor G. G. STOKES, D.C.L., President, in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : — 



I. " The Relationship of the Activity of Vesuvius to Certain 

 Meteorological and Astronomical Phenomena." By Dr. H. J. 

 Johnston-Lavis. Communicated by Professor Judd, F.R.S. 

 Received February 26, 1886. 



(Abstract). 



The determination of the relations, if any such exist, between 

 volcanic activity and certain astronomical or meteorological pheno- 

 mena, cannot fail to throw much light upon the vexed question of the 

 solid or liquid condition of the earth's interior. M. Perrey, as the 

 result of his careful catalogue of earthquake phenomena, believed 

 himself to have proved that these could be shown to have certain 

 maxima and minima, which correspond with positions of the moon 

 in relation to the earth and sun ; there are many considerations which 

 point to the conclusion that great and sudden changes in barometric 

 pressure may be followed by outbursts of volcanic violence; and, 

 finally, if the eruptions of volcanoes, as many geologists believe, are 

 due to water percolating from the surface to a heated magma, rain- 

 fall must have no inconsiderable influence in determining the periods 

 of their occurrence. 



The author of the paper has made use of the opportunity of a 

 residence in the neighbourhood of Vesuvius, to chronicle, according 

 to a scale devised by himself, the varying quantities of vapour emitted 

 from the crater during its usual quiet and continued (Strombolian) 

 stage of eruption ; the period of every new outflow of lava, or of any 

 increase in the flow of lava was also noted. These observations 

 having been carried on daily for a period of one year and nine months 

 — from October, 1883, to June, 1885 — were recorded in tabular form 

 side by side with the moon's quadratures and position in her orbit ; 

 with these are also arranged the daily records of the height of the 



