Reviews — Dr. A. Bruit's Volcanic Researches. 



271 



with iron wire. This method has the advantage of providing as much 

 gas as can be stored. The glass tubes can afterwards be washed to 

 allow of an estimation of the solid material of the fumes. Where 

 haste is essential a vacuum tube can be carried to the desired point, 

 and there opened, charged and resealed. 



Extraction of gases in the laboratory. A vacuum apparatus is 

 employed, and this, with the methods of gas analysis, is described in 

 the book. Very numerous experiments show that such water as is 

 given off is always liberated before the explosion temperature 

 is reached; it is largely dissipated at 150° C. ; at 300° C. there is 

 none left. Certain old volcanic glasses are found to be exceptionally 

 hydrous. 



The main volatile constituents liberated from active rocks at the 

 explosion temperature are — 



Gases. — Chlorine, hydrogen chloride and oxides of carbon. 



Solids. — Chlorides of the alkali metals of ammonium and to a small 

 extent of ferrous iron. 



Sulphur and its compounds are almost always inferior in amount to 

 chlorine and the oxides of carbon. 



Details of the volatile constituents extracted at the explosion 

 temperature in vacuo are given for the lavas of about fifty distinct 

 volcanoes, embracing every part of the earth. The relative proportions 

 vary greatly, as will appear from the following table : — 



With traces of S 2 Cl 2 . 



N-2 and other gases. 



