Dec. 20, 1883] 



NA TURE 



the higher regions of the atmosphere over an area equal 

 to that of Europe. That this is not fanciful is proved by 

 the behaviour of smoke. 1 have often watched when at 

 sea, on a still, calm day, the black s:noke of some passing 

 bteamer rise to some determined height, and then 

 gradually spread itself at an equal and constant distance 

 from the sea like a great flat pall. I have also seen on 

 land the smoke from some manufacturing shaft blown 

 gently by the wind follow the curves of the land, remain- 

 ing always at the same distance trom the ground, but 

 gradually spreading outwaris in every direction. I have 

 also seen two lines of smoke refuse to coalesce, but re- 

 pelling each other exactly as they ought if they were 

 similarly electrified. That smoke is, therefore, negatively 

 electrified I firmly believe, though I have never tested it. 

 Now, that this wonderful atmospheric disturbance was 

 accompanied by extraordinary electrical disturbance was 

 shown, not only by Capt. Watson's observations near the 

 spot, but by Prof. Smith's records at Madras, and hence 

 it requires no great stretch or the imagination to conceive 

 electricity playing a great part in the recent gorgeous 

 display of atmospheric eflects." 



In reference to Mr. Preece's letter, Mr. Crookes 

 writes: — " In a paper read before the Ro>al Society in 

 1879 I showed that at a rarefaction of the millionth of an 

 atmosphere two pieces of electrified gold leaf repelled one 

 another at a considerable angle for thirteen months with- 

 out loss of charge. Therefore at a rarefaction of a 

 millionth (corresponding to a height above the earth's 

 surface of about sixty-two miles) air 1= a perfect non- 

 conductor of statical electricity, without interfering with 

 the mutual repulsion of similarly electrified particles. 

 ■U'hen we bear in mind that the specific gravity of gold is 

 five or SIX times that of the rock whose disruption formed 

 the dust in question, and that the size of the individual 

 particles of dust is certainly many thousand times smaller 

 than my gold leaves, there is every reason to believe that 

 electrified dust, once projected fifty or sixty miles above 

 the earth's surface, might remain there for many years.'' 



Bishop Bromb^", writing to the Times, says that in a 

 letter from a member of his family at Hobart, Tasmania, 

 the writer speaks admiringly of "the loveliest after-glow 

 which was spread over the sky on the other side of the 

 water where the sun had set.'' This was written on 

 October J2 by one who was ignorant that similar pheno- 

 mena haa been obstrved in other parts of the world. 



Another correspondent of the Times states that in a 

 letter dated " Uuem, September 74, 1883," Hicks Pasha 

 wrote: — "By the way, have you in England noticed a 

 large black spot on the sun .'' Today, when it rose, it 

 was of a pale green colour, and we saw through our 

 glasses an immense black spot on the lower half of it. 

 What does this portend ? 1 feel sure there must be some 

 notice of it in the papers in England.' 



Sheriff Rampini of Lerwick, Shetland, writes that 

 the sunsets have been observed in these northern islands. 



Mr. G. F. Burder of Clifton sends the following 

 extract from a letter from a passenger travelling from San 

 Francisco to S>dney, three days after leaving Honolulu. 

 The writer sa) s : — "On Wednesday, September 5, we 

 witnessed a most curious phenotiienon. The sun set 

 perfectly blue, and ne.\t morning it rose a flaming ball of 

 blue The blue light was reflected in our cabins." 



tiN November 30, at 4 p.m., another remarkable sunset 

 was observed in Stockholm. A correspondent states that 

 the western sky became covered with an intense purple 

 after-glow, having the appearance of an enormous distant 

 conflagration, which nearly reached the zenith, and lasted 

 for an hour, even after it was dark, and the stars were 

 visible. On the morning of December i a similar intense 

 light was observed at sunrise. The colour was, however, 

 then more yellow. The phenomena have also been 

 observed in the north of Sweden, in Gothenburg, in 

 Christiania, and in Copenhagen. 



THE KRAKATOA AIR- WAVE 



ON Thursday last Mr. R. H. Scott communicated a 

 paper to the Royal Society giving a map and tabular 

 statements concerning certain barometric disturbances 

 observed towards the end of August last. 



The obvious correspondence of the forms and times of 

 occurrence ot the barometric disturbances, described in 

 Mr. Scott's paper, at once suggested to General Strachey 

 that they were due to a common origin, and the great 

 volcanic eruption at Krakatoa in the Straits of Sunda 

 appeared to supply a probable efficient cause. General 

 Strachey therefore took up the question from this point 

 of view, and at the same meeting communicated a paper, 

 of which the following is an abstract : — 



' ' Any shock of sufficient violence might be expected to produce 

 an atmospheric wave, advancing from the place where it was 

 caused in a circular form round the globe, at first expanding until 

 it had gut half round the earth, and then again contracting till 

 it was again concentrated at the antipodes, from which again it 

 would be thrown back, and so pass backwards and forwards till 

 it was obliterated. It might have been expected that such a 

 wave would travel v\ith the velocity of sound, being probably 

 of the same nature as that "hich causes sound, though 

 the vibrations had not the peculiar character that affects our 

 organs of hearing. It has, however, been suggested to me that 

 the wave may rather have had the character of a solitary wave 

 produced in a liquid, the velocity of whica in the air would not 

 materially differ from that of sound.' 



" A rough examination of the facts at first made known by the 

 observations recorded in Great Britain indicated that there was 

 p7-ima facie strong evidence in support of this view, and that the 

 phenomena would be approximately explained by the passage 

 round the earth of a series of waves travelling at the rate of 

 about 700 milc^ an hour in opposite directions from the place 

 where the volcanic crujlion occurred. The records since pro- 

 cured from other places, and the more c ireful examination of the 

 facts, have quite confirmed this conclusion. 



"Although we may expect to obtain additional data from 

 other parts of the giobe, which will make the investigation of 

 tins somewhat remarkable phenomenon more complete, yet those 

 we now have are sufficient to justify an attempt being made to 

 bring the more important facts before the Royal Society without 

 further delay. 



•' The following table shows the stations from which the records 

 have been received of which u~e has been made in this discussion, 

 with certain particulars of their geographical position, and of 

 their distances inea ured on great circles, from Krakatoa, the 

 place of eruption : — 



Distance frjm Kraka 



toa, measured on a 



great circle 



Toronto : W 



Valencia j ,, 



Coimbra , ,> 



Armagh , ,, 



F.dmouth ,, 



Glasgow ; ,, 



Stonyhiirst ..1 ,, 



Aherdten ,, 



Kew I ,1 



Green" ich 



Paris 



Brussels 



St. Pet rsbarg .. 

 Krakatoa 



79 15 

 10 IS 

 8 24 

 6 39 

 5 4 

 4 It) 

 2 28 



4 20 

 30 zo 



105 22 



N. 43 40 



,, 51 55 



,> 40 '3 



., 54 21 



,, 5'J 9 



.. 55 53 



,. 53 5' 



,, 57 10 



,, 51 28 



,. 5J 29 



„ 48 50 



.. 50 5 1 



-. 59 5"^ 



S. 6 9 



217 45 

 no 29 

 112 2 

 >o7 43 

 107 45 

 106 3 

 105 26 

 >04 35 

 104 33 

 104 21 

 103 II 

 loi 43 

 87 57 



■ The log of a 5U 

 that the explosi ns 



veying ship 



: heard in Ceylon, 



t ihe north of Borneo, snce received, sh'iws 

 ere on the morn.ng of August 27, at a dis- 

 ino ; an i it fias been also stated that these 

 i distance of about 2000 miles. — R.S. 



