October 2, 1885.] 



SCIENCE. 



293 



huge masses of earth piled up the vast waves which 

 swept with such destructive force upon the islands of 

 Java and Sumatra, and destroyed forty thousand 

 human beings. Some lesser explosions were heard 

 during the rest of the 27th, and the day of the 28th. 



Scarcely any thing is known of Krakatoa before this 

 eruption ; but there are records of a similar, though 

 less extensive, eruption in May, 1680. For two 

 hundred years it has fallen into an uninterrupted 

 sleep to be awakened with such terrible violence 

 in 1883. At the time of the eruption it was un- 

 inhabited. There are certain legends handed down 

 by the natives of the neighboring islands from which 

 we can see that the existence of Krakatoa as an 

 eruptive volcano antedates Javanese heroic history. 



The travellers had little ditficulty in landing on the 

 extreme west of the cliff, on the shores of a small in- 

 let following a deep ravine newly eroded by the rain 

 through both the light material recently ejected, and 



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PU>IICE FOUND FLOATING FIFTEEN MILES FROM MADAGASCAR, 



AUG. 13, 1884 (La nature). 



the underlying older solid lava-beds. The ashes at 

 this place were from sixty to eighty metres in depth, 

 and were well separated from the black and gray lava 

 by their white color. Although more than nine 

 months had elapsed since this matter had been thrown 

 out, still, in some places, it was so warm that steam 

 escaped from among the ashes, leaving a layer of sul- 

 phur and sal-ammoniac behind. A bituminous odor 

 was also noticeable, and this was no doubt due to the 

 dry distillation of the vegetation buried beneath the 

 warm cinders. After taking photographs, they left 

 the island, and proceeded toward Lang and Verlaten, 

 two small islands, probably a part of Krakatoa torn 

 asunder during some remote eruption. These islands, 

 like all their neighbors, are covered with a mass of 

 pulverized pumice thirty metres deep, furrowed by 

 the rain. The aspect of the islands reminds one of the 

 front of certain glaciers; but the temperature of 

 40° C, due to the absorption of the sun's heat, will 



not allow this deception to last long. The surface of 

 these two islands is much increased by the piling up 

 of material on their sides during the eruption. To 

 counteract this increase of surface, an island, 

 Poolsche Hood, which was situated to the east of 

 Yerlaten, and a reef, Polish Hat, which rose to the 

 west of Lang, have disappeared. Save the escape 

 of steam, mentioned above, and which is independ- 

 ent of volcanic activity, absolute tranquillity reigns 

 in these desolated regions. There are neither fumer- 

 oles, nor jets of vapor under pressure, which gener- 

 ally persist a long time after the eruptive period. 

 The natural equilibrium is re-established. But it is 

 to be remembered that the fires merely sleep, and that 

 probably some day they may awake from their leth- 

 argy. 



In conclusion, it may be well to give a brief account 

 of the geological structure of Krakatoa and the neigh- 

 boring islands. The series of volcanic islands to 

 which Krakatoa belongs, follows a line extending 

 N.N.W., obliquely across the straits of Sunda, and 

 forming an angle with the lines of the principal vol- 

 canoes of Java and western Sumatra. The point 

 where these three lines meet is found approximately 

 at Krakatoa. The base of the island is made up of 

 solid columns of a crystalline basalt, and of augite 

 and labradorite, all very basic, and in which pyroxine 

 augite made an abundant part of the second consoli- 

 dation. These basic formations have been found at 

 Krakatoa, Sebuku, Protection, and Sebesie. Above 

 these various basaltics is a compact column of ande- 

 site, becoming more and more acid in its upper part, 

 and nearly barren of the microliths of augite which 

 are abundant near its base. There are layers of 

 pumice between the sheets of lava, showing that the 

 eruptions of the volcano have been of two kinds suc- 

 ceeding each other. 



The ashes ejected by the last eruption are composed 

 principally of a light spongy pumice, and of irregular 

 blocks of a compact dark glass, in which may be dis- 

 tinguished the brilliant crystals of labradorite. This 

 acid glass (70-72 in a hundred parts of Si.) presents 

 a very simple constitution. It contains a good num- 

 ber of crystals (first consolidation) of labradorite, 

 augite, hypersthene, and titaniferous oxide of iron; 

 also elements of the second consolidation in the form 

 of felspathic microliths, attributable to oligoclase. 

 In addition to these truly volcanic matters, we may 

 mention some debris in terrains, composed of frag- 

 ments of quartziferous diorite, and balls of a calcif- 

 erous marl, regular, and polished by erosion with 

 pumice. These debris products are relatively rare; 

 and, to all external appearance, the islands are one 

 mass of volcanic ash. 



TOUGHENED GLASS.^ 



Upoin' investigating the De la Bastie invention of 

 the so-called toughened glass, Mr. Frederick Siemens 

 has found that the process is not a manufacturing 

 process at all, but, rather, a somewhat impracticable 



1 Condensed from a paper read before the Society of arts, 

 London. 



