138 CARNEGIE INSTITUTION OF WASHINGTON. 



which lasted but 40 minutes, there has been nothing especially worthy 

 of investigation at the Sicilian volcanoes. Field research has thus 

 been limited to the neighborhood of Naples, i. e., to Vesuvius, the Sol- 

 fatara, etc. 



A veiy interesting lava tunnel, of the intumescence type, has been 

 found on the lava of 1858, and a description, with photographs by me, 

 is soon to be pubhshed by Dr. Malladra. The interior was photo- 

 graphed by the light of an acetylene hand lamp with reflector, and 

 shows the advantage of this form of artificial illumination over the 

 ordinary flash-light. The picture shows a last little stream of pahoe- 

 hoe lava which had flowed from the mouth on to the floor of the tunnel. 

 There are also tree-molds, of small size, in that neighborhood. 



Since April there has been no flow of lava in the crater of Vesuvius, but 

 Dr. Malladra and I decided to make another descent on August 2, in 

 order to compare conditions at the crater bottom with those prevaihng 

 at our last descent on August 4, 1916. The date was chosen on the 

 basis of luni-solar positions, which influence was effective. Again the 

 night was spent at the bottom of the crater, the entire stay being 15 

 hours. The eruptive conelet remains at the same height above the 

 sea, but the crater bottom has been greatly filled up around it by lava 

 which emanated from it and from a second conelet which has arisen 

 over what, at our last descent, was a funnel depression near the base 

 of the main conelet, and which we at that time agreed was destined 

 to be a new vent. This second cone emitted several streams which 

 were all of ''aa" lava, and is now reduced to vapor emission. The 

 lava in the conduit of the main eruptive conelet has returned to the 

 ultra-liquid condition which was characteristic of the first year of the 

 opening of the conduit (1913). At the time of our last descent there 

 was sufficient viscosity for the formation of bombs. It now boils 

 quietly wdthin the cone, with now and then a throwing out of liquid 

 fragments, of which samples have been sent to the laboratory. The 

 general condition of the crater bottom is quite Hawaiian, with hum- 

 mocks covered with lava splashes and some enormous intumescences 

 which have Ufted the crust of the floor to heights of 10 or more meters, 

 showing a tendency to ramify from the main conduit of the eruptive 

 conelet. The lava filling the great crater has now reached a sufficient 

 height to make possible the initiation at any moment of an external 

 lava flow of the slow tvpe, such as characterized the last eruptive 

 period (1875-1906) in the years 1881 to 1883, 1885 to 1886, 1891 to 

 1894, 1895 to 1899, and 1903 to 1904. 



Conditions within the crater were bad as regards gas and photo- 

 graphs were made with the utmost difficulty, but through a process 

 of redevelopment these have been brought out as strong and clear as 

 any and the complete documentation has thus been successfully accom- 



