Dec. 20, 1883] 



NA TURE 



175 



banks. Indescribable was the confusion into which 

 prahus, steamboats, and tambangans were thrown in the 

 lower city, and no pen can depict the confusion m old 

 Batavia, resulting in especially the natives and Chinese 

 seeking safety bv a general flight. To give some idea of 

 the tidal waves which agitated the sea and rners, we need 

 only sav that at Tanjang Priok, in particular, the water 

 rose ten feet within a few minutes, that it not only wholly 

 overflowed a portion of Lower Batavia quite suddenly, 

 but also bore fully laden prahus of twenty-five lasts and 

 e\en more capacity ashore like straws. This phenomenon 

 was repeated at 2 p.m., but not so violently. However 

 great was the force exerted by this heavy flow, there came 

 a moment, after it had raged its utmost, when the water 

 in masses of immense height suddenly ebbing away 

 vanished, and left the river beds and sea bottom a while 

 dry. Meanwhile, the thick, heavy, and oppressive atmo- 

 sphere, charged with sulphurous fumes, began to clear up 

 somewhat in spite of the cold. It became lighter, and by 

 the increasing light people beheld a sight seldom certainly 

 witnessed here in the course of centuries. The streets, 

 or rather the roads, the trees, and the houses, were covered 

 with a wholly white layer of ashes, and presented in the 

 land of the sun a genuine Dutch winter scene. In the 

 meantime,vwhen, later in the day the distant detonations 

 had ceased and rumbles had become fainter, no one had 

 yet the least idea of the havoc wrought by this strange 

 natural phenomenon. By that time Anjer had been 

 flooded and devastated by tidal waves ; with few excep- 

 tions its inhabitants had been drowned in a moment of 

 time, and on its site in the course of that disastrous 

 Monday nothing but an extensive muddy morass could 

 be seen." Editor 



We have received the following communications : — 



Early in the morning, on December 13, between four 

 and five o'clock, a violent tempest from the north-west 

 arose. The temperature in the course of the morning 

 was rather low, viz. 4^ C, and, especially between six and 

 seven, the wind was accompanied by showers of rain, 

 intermingled with hail. This rain was of a peculiar 

 nature, every drop, after having dried up, leaving behind 

 a slight sediment of grayish coloured substance. This 

 was most distinctly to be seen on the panes of windows 

 turned towards the west or the north-west : the spots 

 with which these panes were dotted did not leave the 

 least doubt about their having been caused by the fallen 

 rain. 



The streamlets of rain, having evaporated, left on the 

 whole surface of the windows the said grayish matter 

 behind, so that there can be no doubt but the rain itself 

 had conveyed from the upper air the above dust. 



The magnificent "cloud-glow ' which, on several pre- 

 vious evenings, had also been obseived hereabouts, and 

 which has been attributed by meteorologists — with good 

 right, no doubt — to the volcanic ashes due to thecatastrophe 

 of Java, made us suppose that the substance observed by 

 us on the windows could not but be of the same origin. 

 We took it for granted that whirlwinds, when the storm 

 set in, had brought the dust down to the lower regions of 

 the atmosphere, where it mingled with the falling rain. 

 Consequently we proceeded to examine microscopically 

 the sediment, in order to compare it with original ash 

 from Krakatoa, which had been sent to the Agricultural 

 Laboratory at Wageningen to have its value as plant-food 

 ascertained. The result of this examination was that 

 both the sediment and the volcanic ash contained (i) 

 small, transparent, glassy particles, (2) brownish, half 

 transparent, somewhat filamentous, little staves, and (3) 

 jet black, sharp edged, small grains resembling augite. 

 The average size of the particles observed in the sedi- 

 'oect was of course much smaller than that of the con- 

 stituents of the ash. These observations fortify us in 



our supposition, expressed above, that the ashes of 

 Krakatoa have come down in Holland. 



Wageningen, December 14 M. W. Beyerinck 



J. VAN Dam 



With every spare cranny in Nature filled with vol- 

 canic dust, and the whole discussion in far abler hands 

 than mine, I should be loth to trouble you, were there not 

 one point in connection with the recent optical pheno- 

 mena which has, as far as I know, escaped observation, 

 and which may possibly be worthy of consideration. I 

 allude to the connection between the sky-glows and the 

 phenomenon commonly known as " Rayons de Crepuscule." 



To the latter phenomenon I have incidentally had 

 my attention much drawn, having been for many years 

 engaged in a set of cloud observations for a special pur- 

 pose. This appearance has already been described, and 

 to some extent discussed, in the pages of Nature and 

 elsewhere. Several other phenomena, some of theni 

 occurring while the sun is above the horizon, seem to 

 have been confounded under the same name. That of 

 which I now write consists of red rays converging 

 to a point near the horizon opposite to the sun's 

 position, usually at between fifteen and fifty minutes 

 afier the sun has set or before it has risen. On 

 rare occasions I have seen these belts in the evening 

 ext. nding past the zenith so as to converge towards the 

 position of the sun beneath the western horizon. The 

 inter-^paces of these rays (which, as has long ago been 

 explained by Mr. Lockyer, are the shadows of hills 01 

 clouds beyond the visible horizon) are often of a comple- 

 mentary blue-green. The colour of the rays is similar to 

 that reflected at an earlier hour in the evening, or at a 

 later in the morning, from the most elevated cirri. This 

 ]5henomenon seems to be in itself almost entirely inde- 

 pendent of any weather conditions, occurring under 

 utterly diverse states of the atmosphere. It possesses 

 one remarkable characteristic. It is far more common, 

 in Europe in the month of November than at any other 

 period of the year, although the prevalent state of our 

 November skies is scarcely such as to favour its visibility. 

 To this characteristic I called the attention of some scien- 

 tific friends several vears ago, amongst whom I may 

 mention the name of Robert H. Scott, F.R.S. I have 

 thought that the "Rayons de Crepuscule'" were some- 

 what more common in the years when the November 

 meteors were most abundant. But if this prove to be 

 the rule the exceptions are numerous. There are long 

 periods during which there are no "Rayons de Cre- 

 puscule'' or in which if they occur our view of them is 

 entirely obstructed. I have always supposed that 

 the fall of meteoric dust determines the condensation andJ 

 congelation of the vapour which exists in those strata 

 from which these red rays are reflected, just as London 

 smoke determines the formation of spherules of fog. The 

 solsr rays are thus reflected from ice spiculae suspended, 

 in the atmosphere, rather than^ as I understand Prof.. 

 Briicke to imply, from the atmosphere itself. Are there 

 any reasons for doubting the possibility of the existence 

 of much water vapour at a far greater elevation than 

 this stratum? This would ordinarily remain in the vapour 

 state, being above the ordinary range of the pulverised 

 meteorites. 



Now the same orange-red glow in the east, from ten to< 

 twenty minutes after sunset, by which I have usually been. 

 able to predict the appearance of " Rayons de Cre'pus^ule,'' 

 has been almost constantly visible at that hour through- 

 out the present period. Further, this has been followed 

 slightly on one, and vividly on two, of those evenings 

 when the succeeding glow was most remarkable, by the 

 ^^ Rayons de Crepuscule" themselves. And the rays of 

 red light emerging on several occasions from the effulgent 

 glow in the west appear to me closely to resemble 

 western continuations of very elevated "Rayons de 

 Crepuscule." 



