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



The solfatara are found to be increasingly hot according as one 

 approaches the centre of the hillock mentioned above. At a distance 

 warm streams and springs occur. At 300 metres from the centre 

 springs at 92° C. were met with, and so on until further advance was 

 precluded owing to hot penetrating acid fumes emitted at a temperature 

 of 270° C. 



Leaving out of account the many interesting phenomena connected 

 with the deposition of sulphur, and in the high temperature zone of 

 realgar, we shall restrict our attention to the pressure of the water- 

 vapour in these solfatara. From 92° to 120° C. the vapour pressure 

 of the water mounts rapidly; from 120° to 270° C. it falls no less 

 rapidly. There is no support, therefore, for the common idea that the 

 source of heat is the source of water. 



At the time of Brun's visit in 1908 Tjividey, another Java volcano, 

 was supplying a diagrammatic vindication of his views regarding 

 solfataric water. A cold stream leapt into the warm central region 

 of the crater, and scattering on the little solfataric plain, emerged 

 steaming and charged with milk of sulphur. Other examples are 

 cited where crater lakes have established themselves, and these too 

 are useful in driving home the argument. 



And now for Kilauea, the most obliging of volcanoes, paroxysmal 

 and yet not dangerous ! 



Brun's first experiment consisted in sucking up the fumes from the 

 crater pit through the glass tube system already described. Salts 

 were deposited along the whole length of the tubing, but no trace 

 of moisture. 



His second experiment was even more striking. He took a series 

 of dew-point readings within and without the great white cloud as 

 the latter drifted across the rim in a steady stream carried by the 

 prevailing trade-wind ; his results, expressed in curves, show in every 

 case a lower dew-point for the air entangled in the cloud than for the 

 normal atmosphere outside. He also collected specimens from the pit 

 itself in vacuum tubes, and, testing them later on in the laboratory, 

 found a like deficit in regard to water. Leaving the rim of the pit 

 he next visited one of the peripheral aqueous fumaroles, situated, as 

 at Semero, where the volcanic heat travelling outwards meets the 

 general pluvial moisture of the mountain mass. Here he obtained, 

 as was to be expected, exactly the reverse result, to wit, a markedly 

 elevated dew-point. 



The lowering of the dew-point in the great white cloud of Kilauea 

 is an observation which cannot long go untested. Meanwhile it is 

 difficult to see how a mistake can have crept in to vitiate a whole 

 series of experiments. Brun naturally interprets his result as a further 

 proof of the anhydricit}'' of volcanic emanations; the lowered dew- 

 point is the result of dilution of the air with anhydrous gases carrying 

 hygroscopic solids in suspension. 



One last observation regarding the great white cloud of Kilauea 

 may be recorded alike on account of its beauty and its quaintness. 

 A photograph is published showing the author's shadow thrown by 

 strong sunlight on to the cloud, and he assures us that, when he took 

 this photograph, there was no encircling halo round the image of 



