Reviews — Dr. A. Brun's Volcanic Researches. 318 



layer of ferrous chloride, and has a temperature of about 140° C. 

 Below there occur black lapilli covered with a white saline crust. At 

 60 cm. the temperature is already 360° C. 



There are no fumaroles. Burying the tubes as deeply as possible 

 in the lapilli, the gas pumped up proved to be nothing but air with 

 a trace of carbon dioxide and ammonia. The dew-point of the air 

 thus obtained was 16° C, that of the atmospheric air at the same 

 locality 16°-5 C. This experiment, and the preservation of the ferrous 

 chloride on the lapilli, afford evidence that the volcano, though hot, 

 is exhaling no water. As it is scarcely exhaling any vapour or gas 

 at all this observation is in a sense negative, but it can scarcely be 

 doubted that were Timanfaya transported to a humid region it would 

 give rise to the commonplace solfataric phenomena. 



Once again the scene changes as we follow our explorer to the 

 soaking tropical region of Java. As before only a few selected 

 observations can be mentioned. The giant Semero is climbed. The 

 destructive deluges of mud which descend its slopes are only indirectly 

 volcanic in origin. Since its recent reawakening Semero has cleared 

 its upper slopes of vegetation and thus has given a free hand to 

 pluvial erosion. 



The great white cloud of the volcano slowly drifts out of sight 

 beyond the horizon. It is insoluble in the atmosphere and therefore 

 consists of solid particles, not of condensed water-vapour. This is 

 a point Brim emphasizes repeatedly in connexion with active 

 volcanoes in general. It has, however, long been noticed that the 

 appearance of Stromboli and Vesuvius is markedly dependent upon 

 weather condition, and Brim in a later portion of his book alludes to 

 this phenomenon, accounting for it by postulating a condensation of 

 atmospheric water on hygroscopic salts contained in the anhydrous 

 fumes. A critic may well ask : if the salts in the fumes can on 

 occasion condense atmospheric water, can they not also be relied upon 

 to condense and retain the magmatic water with which, according to 

 orthodox opinion, they are closely associated? It seems wise, then, 

 not to rely too far upon the insolubility of the great white cloud as 

 seen from a distance. Brun's researches carried out actually within 

 the cloud at Kilauea are therefore all the more welcome, but before 

 we can deal with these there are other points to notice in regard to 

 Semero and its Javanese companions. 



Semero itself was in a paroxysmal phase when visited. The rim 

 bathed in fumes gave rise to no aqueous condensation, although its 

 surface temperature, observed at 7 o'clock in the morning, was only 

 5° C. The ashes fell perfectly dry. Aqueous fumaroles were noticed, 

 but they had no deep roots ; they occurred at the junction-line of the 

 dry region round about the active foci and the moist plateau region 

 beyond. Their fumes dissolved freely in the air. 



Papandajan furnishes a striking instance of the solfataric phase. 

 The crater has a vast undulating floor cut up by stream channels and 

 surrounded by a wall 100 to 300 metres high, breached at the east by 

 the eruption of 1772. The hottest solfatara occur on a little hillock 

 built up of broken pebbles of old lavas much altered ; pure opal has 

 frequently been produced at the edge of this hillock. 



