160 Proceedings, &c., for 1885. 



to form an adequate idea of the immense area over which the 

 sound travelled, a circle should be drawn round Amsterdam with 

 a radius of 30 degs., commencing at the most northern point, 

 at 82 degs. N. lat.j also north of Spitzbergen ; then across 

 Nova Zembla, along the Ural Mountains to Orenburg, Tiflis, 

 Damascus, Jerusalem, Suez, crossing the Tropic of Cancer at about 

 15 degs. E. long. (Greenwich); then to the most southern 

 point at 22 degs. N". lat. in the Desert of Sahara, crossing 

 once more the Tropic of Cancer at 5 degs. W. long. (Greenwich), 

 close along Terro; then to the Canary Islands and the Azores, 

 and back to Spitzbergen through the greatest portion of 

 Greenland. It was observed that the reports were heard more 

 distinctly at a distance than at places nearer in the same direction 

 with Krakatau, as Anjer, Serang, Batavia. This phenomenon is 

 attributed to the fact that in the lower strata of the atmosphere an 

 immense quantity of ashes was existent, which could not but have 

 the effect of deadening the sound. There is every probability that 

 along and over this, ash-cloud the sound travelled to more distant 

 places — as, for instance, Batavia (ninety miles from Krakatau) — 

 whilst at Anjer, being behind this ash-cloud, the sound was only 

 feebly heard. At the time of the eruption waves of air of great 

 length, although not audible, had a remarkable effect. The more 

 rapid of these vibrations affected, as a matter of course, the 

 buildings and the walls of rooms, so that objects against the walls 

 or hanging from the ceiling began to move, and this accounts for 

 the fact that at Batavia and Buitenzorg, at a distance of 150 kilo- 

 meters from Krakatau, door and windows began to shake, the 

 clocks stood still, and statuettes on the cupboards fell down, 

 whilst oil-lamps came down with a sudden crash. At other places 

 a similar effect was experienced, solely arising from the vibrations 

 of the air, and not from earthquakes, which were never experienced 

 with any certainty during the whole time of the eruptions. This 

 is a most remarkable event. Moreover, the most terrific explosions 

 produced air waves of an immense length of wave. From 

 barometrical observations in Europe and America it was ascer- 

 tained that the rapidity of these waves nearly equalled the 

 rapidity with which sound is propelled, showing that it would take 

 seven minutes for these waves to reach Batavia from Krakatau. 

 The most terrific explosions took place on the 27th of August at 

 thirty-five minutes past five, ten minutes to seven, five minutes past 

 ten, and five minutes to eleven, Batavia time. The explosion of 

 five minutes past ten was the fiercest, when an enormous air-wave 

 ascended from the top of Krakatau, and in the form of a ring 

 round that point spread along the surface of the earth, and 

 travelled 3^ times the entire circumference of the earth. The 

 rapidity, as already stated, was nearly that of sound, although 

 the waves were of a gigantic length (the length of wave of the 



