106 GEOLOGY 



GEOLOGY' 



Volcanoes. Long-continued study of volcanic phenomena in various parts of the 

 world, supplemented by much chemical and physical research in the laboratory, has led 

 Dr. Albert Brun, of Geneva, to certain conclusions, which, if confirmed, will modify 

 profoundly the generally accepted views on vulcanism (Recherches sur V Exhalaison 

 volcanique. Geneve, 1911). From observations in the Mediterranean region, the 

 Canary Islands, Java, Krakatoa and Hawaii, Dr. Brun believes that during a paroxys- 

 mal eruption no water is exhaled from the volcano. Examination of the gases evolved 

 during an outburst at a high temperature invariably failed to show either water-vapour 

 or the dissociated elements of water. 



The great white cloud, which is so characteristic a feature of a volcano at its maxi- 

 mum temperature, is said by the author to be composed, not, as commonly assumed, of 

 water-vapour expelled from the volcano and partially condensed on meeting the atmos- 

 phere, but of solid anhydrous particles of extreme tenuity, associated with certain dry 

 gases. The solid matter consists chiefly of the chlorides of potassium, sodium, ammoni.- 

 um and iron, with ammonium fluoride and very finely divided silica. When the exhala- 

 tion encounters the atmosphere, some of its hygroscopic salts may condense moisture, 

 and in this way the erupted products may become more or less hydrated; but the water 

 thus acquired is meteoric, not volcanic. In fact, the volcano instead of contributing 

 water to the atmosphere subtracts water from it. It is notable that Dr. Brun's observa- 

 tions at Kilauea, in 1910, showed that the dew-point in the interior of the white cloud 

 was lower than in the surrounding atmosphere. It was also noticed in Hawaii that the 

 shadow of an observer projected on the white cloud was not accompanied by any trace 

 of a glory, such as might have been expected had the cloud contained water-particles. 

 Moreover, the volcanic vapours drawn through cold tubes deposited no moisture. Dr. 

 Brun therefore concludes, contrary to general belief, that all paroxysmal eruptions are 

 essentially anhydrous. 



It is true that the vapour of water is present at low temperatures in the exhalations 

 from certain fumaroles and solfataras, but it is maintained that such water is not derived 

 from volcanic sources. It is practically pluvial water, its amount depending chiefly on 

 the climate and on the capacity of the volcano to collect water from the atmosphere. 

 Many igneous rocks yield water-vapour when heated to a moderate temperature, but 

 it is held that this has been absorbed by the rock after cooling. Dr. Brun belie'ves that 

 whatever gases may be obtained from rocks on heating them to about 600 C. are simply 

 gases that have been so absorbed and are therefore not of true volcanic origin. 



According to Dr. Brun, the nitrogen of lavas exists mostly as nitride of silicon, which 

 he terms Marignacite, after Prof. Galissart de Marignac, of Geneva. The only volcanic 

 nitride previously recognised had been that of iron. 



Etna. An eruption of Etna, of short duration but exceptional severity, occurred in 

 1911, and was the subject of scientific study by Prof. A. Ricco (Bollettlno d. Soc. Sis- 

 mologica Italiana, vol. xv, p. 273) and Prof. Gaetano Platania, of Catania (Rivista 

 Geografica Italiana, Anno xix, Fas ; 7). Evidence of approaching activity had been 

 observed for several months in the early part of the year, and on May 27 the serious 

 disturbance commenced by the opening of a vent in the upper part of the central cone, 

 on the N.E. side. The activity culminated on September 10, resulting in the forma- 

 tion of a radial fracture, about five miles long, running in a N.E. direction. From 

 numerous vents which opened along this line, cinders were thrown out in enormous 

 quantity, forming a long chain of cones. Altogether no new vents are said to have 

 opened. Lava was also extruded in two streams, partly blocking the Circumetnean 

 railway, in places nearly 100 feet high. The eruption ceased after about a fortnight, 

 though earthquake-shocks continued for a time. 



Vtdcanological Institute. In accordance with a suggestion by Sig. Immanuel 

 Friedlaendir, of Naples, at the International Geological Congress held at Stockholm in 



1 For E. B. articles on Geological Subjects, see Index Volume p. 913. 



