Reviews — Dr. A. Bruit's Volcanic Researches. 269 



3. The maximum temperature of a lava containing plienocrysts is 

 given by the melting-point of the most fusible among these pheno- 

 crysts (e.g. 1,230° C. in the case of the augite plienocrysts carried by 

 the lavas of Stromboli and Etna). 



4. The maximum temperature possible for a volcano is fixed by the 

 ' explosion temperature' of its magma, that is, by the temperature at 

 which its magma emits gas sufficiently rapidly to undergo a sudden 

 expansion. Acid lavas have a sharply marked explosion temperature ; 

 basic lavas, which are more fluid, begin to give off gas to an appreciable 

 extent as soon as they soften, and by careful heating it is possible to 

 avoid actual explosion. 



The laboratory determinations of temperature referred to above can 

 be supplemented in the field, and this becomes essential in the 

 investigation of fumaroles. The methods employed in such cases are 

 given in outline in the book. 



The results of about seventy experiments dealing with the 

 temperature constants of minerals are tabulated. In keeping with 

 the almost aggressive self-reliance of the author the recent work of 

 the American school is not taken advantage of ; this is unfortunate, 

 and one has to turn to the original papers to realize the following 

 correspondences : — 



Anorthite. Melting-point (°C). 



From Idsu, Japan . 1,490, 1,510, 1,520 (Brun, 1902). 

 Synthetic . . . 1,544, 1,547, 1,550, 1,562 (Brun, 1904) ; 1,532 



(Day & Allen, 1905). 

 Albite. 

 FromViesch . . 1,250 (Brun, 1902). 

 Synthetic . . . 1,230 (the value obtained by extrapolation ; no 



definite melting-point ascertainable, ' melting ' 



being spread over a temperature interval of about 



150° C. ; Day & Allen, 1905). 

 Pseudo-Wollastoriite . 1,515 (Brun, 1904) ; 1,512 (Allen & White, 1906). 



These results show that Brun was much in advance of his time in 

 the accurate determination of geophysical temperate constants. In 

 other cases where comparison is possible there are somewhat important 

 discrepancies; these are no doubt due in part to chemical peculiarities 

 in the naturally occurring minerals experimented on by Brun, but 

 their occurrence makes the omission of the American data all the more 

 regrettable. 



The results of thirty-five temperature experiments with lavas may 

 ,be illustrated by giving two examples. 



Kilauea. Basaltic glass with very few crystals. On account of this 

 scarcity of crystals the lava is extremely fluid at moderate temperatures ; 

 at the same time, to obtain initial deformation one must heat to 

 a higher temperature than in the case of lavas from other volcanoes : 

 up to 1,100° C. the colloid is unusually resistant, but above this it 

 becomes very fluid. According to different experiments the temperature 

 of formation of a ropy surface is 1,072° C. or 1,073° C, and the 

 temperature at which the lava flows freely with emission of gas is 

 1,1 16° Cor 1,159° C. The "hairs of Pele" format 1,120°-1,160° C. 



Kralatoa. Green obsidian mixed with the pumice of 1883. The 

 explosion temperature for any particular specimen is very well 



