13' 



Feb, 23, 1887, and the great Charleston earthquakes of Aug. 31,. 

 1886, were described as illustrative of seismic phenomena in 

 general. The connection between seismic disturbances and volcanic 

 outbursts was brought prominently forward, and illustrated by the 

 phenomena witnessed in New Zealand on June 10, 1886, which 

 destroyed the Sinter Terraces on Lake Kotomahana. A full' 

 description was then given of the sequence of events during the 

 great eruption of Krakatoa in August, 1883. 



Having thus referred to recent illustrations of terrestrial 

 activity, the Lecturer turned to the detailed study of volcanic 

 phenomena. He showed that the essential function of a volcano 

 was to establish a communication between the exterior of the earth 

 and its interior, and through the channel thus opened up, heated 

 matter was brought to the surface. A volcano was defined as 

 "a natural apparatus for turning the earth inside out." In this 

 process of bringing matter from the interior of the earth and 

 depositing it upon the surface, water in some form or other plays a 

 most important part. The geographical distribution of volcanoes 

 was traced, their linear arrangement marked, and their proximity 

 to the sea dwelt upon. The action of superheated steam was 

 regarded as a prime factor in the production of volcanic phenomena. 

 The evolution of steam from Stromboli and the discharge of steam 

 forming the "pine-tree appendage" of Vesuvius, were described. 

 Among other vapours and gases emitted from volcanoes are cited 

 hydrochloric acid and various volatile chlorides, sulphuretted 

 hydrogen, sulphurous acid, carbonic acid, free hydrogen and 

 nitrogen, ammonia, and boric acid. The Solfatara, near Naples,, 

 was referred to as a volcanic vent in a lingering stage of activity,, 

 exhaling only vapours. 



Turning to the liquids concerned in volcanic phenomena,, 

 water was mentioned as the chief body ejected by geysers. The 

 nature of mud volcanoes was referred to. The principal liquid 

 product in most active volcanoes is of course lava, or molten rock. 

 Its composition, temperature, and physical properties were described, 

 and its behaviour in cooling was noted. The formation of Pele's 

 hair, volcanic bombs, and the common characteristic forms of lava,, 

 was discussed. 



