Jan. lo, 1S84] 



NA TURE 



251 



precede the fall of meteorite-; being of a distinct nature from 

 those which accompany the periodical swarms of shooting stars, 

 and tliereliv manifest their cosmical origin. As far as I know 

 there does not exi:-t a connection, which might be expected by 

 the Usual theory, between these periodical swarms and increased 

 frequency of stone-falls ; on the other hand, it is evident that 

 the laie extraordinary manifestations of volcanic activity mu^t 

 fiu-nish a crucial te.-t for the hypothesis in que^tion ; if it were 

 right, there mu-t be expected an augmented fall of meteorites to 

 follow this period of dust-spreading. D. Wetterh.^n 



Freiburg, Badenia, January 5 



Amongst the many interesting points for consideration in 

 connection with the late sunset phenomena is the very general 

 prolongation of twilight produced by them, doubtless from the 

 reflection of the sun's rays from clouds or diftused vapour at 

 a more than ordinary elevation, after the sun hid set to 

 all at a lower level. In reference to this subject, Mr. 

 I",. Douglas Archibald states that he estimated the height of a 

 glowing stratum [i.e. diffused clouds) as from ten to thirteen miles ; 

 that Miss Ley, from calculation, had given thirteen miles as the 

 height of a similar cloud, and in continuation he says : — " I 

 think this height is far more probable than forty miles, as calcu- 

 lated by Prof. Ifelmholtz. Besides, can we imagine either 

 vapour, or volcanic dust, or a mixture of both, to be capable of 

 remaining in suspension in the air of such tenuity as must exist 

 at such au altitude?'' (Nature, December 20, 1883, p. 176). 

 To this question I would reply by another, and ask if we can 

 imagine vapour or volcanic dust to be capable of remaining in 

 suspension in air of some 17,000 limes less density than water, 

 as at thirteen miles, high, that is about the calculated compara- 

 tive density of the two. 



Or I will go farther, and ask if any one can imagine that 

 water, w hich is about S60 times heavier than the air at sea-level, 

 can be suspended in the atmosphere without the aid of some 

 buoyant power. 



A theory on the cause of rain, storms, the aurora, &c., which 

 I submitted to the British Association at the Glasgow Meeting, 

 1S40 (<ee Repor;), was briefly as follows : — 



"That, as electdcity cnats the surface of all bodies, occupies 

 space, and has no weight, in evaporating, the minute particles of 

 water take up electricity in accordai ce with their surface and 

 temperature, and are buoyed up into the atmosphere by it, where, 

 if condensed {i.e. cooled), their capacity for electricity is reduced, 

 and the surcharge is retained or passes away in accordance with 

 the conducting or non-conducting state of the atmosphere. I 

 cannot go further into particulars in this paper, but I may say 

 that I have no knowledge of any phenomenon connected with 

 the cause of rain which is not explicable in accordance with the 

 theory, although forty years' exertion has not enabled me to 

 bring it fairJy under con ideration. 



In my first paper I suggested, as a test for the theory, that 

 conductors should be raised from the earth to the regions of the 

 clouds, under tte idea that the withdrawal of electricity by this 

 means would produce rain in temperate, and the aurora in frigid 

 regions. And I hold that 1 am fully borne out on both these 

 points by Prof. Lemstrbm's grand auroral experiment ; as, on 

 the connection beiuij made between the wirewoik on the top of 

 the mountain and the earth at the foot of it, electric currents 

 were observed, the aurora became visible, and the formation of 

 ice on the wiresvork was so heavy as to break it down ; thus 

 showing that rain w-ould have fallen if the experiment had been 

 tried in a lower latitude. I hold also that the experiment already 

 proves that electr.city is the buoyant power of vapour in the 

 atmosphere. 



With respect to the undoubted great elevation :if vapour and 

 volcanic dust thrown up by the Java eruption, I have long been 

 led to believe that electricity coats the surface of bodies in ac- 

 cordance with their temperatures, and that the non-burning 

 property of superheateil metal is from the intense force with 

 which electricity coats the surface, and thus the hand is not 

 actually in coniact wi h the metl when placed upon it ; and in 

 the case of effluent high-pressure steam, I believe Ihe particles 

 are so completely wrapped up in their coatini;s of electricity 

 that they do not touch the object the steam impinges on. bear- 

 ing these points in mind, it may easily be imagined that par- 

 ticles of dust or water as vapour, when cast up from a volcano, 

 may be at the highest conceivable temperalure, and charged 

 with electricity in a like degree, and that, being driven up by 

 currents of hea ed air, the particles may rise to an elevation far 



above that of ordinary vapour, and may remain suspended there, 

 more or less, in accordance w-ith the non-conducting condition 

 of the atmo^phere at such elevations. G. A. KowELL 



Oxford, January 2 



Amongst the many int- resting questions raised by the discus- 

 sion on the recent sun-ets, not the least interesting is the questici: 

 of the upper cu rents of the atmosphere. Mr. Norman Lockyer, 

 in bis article in the Times of December 8, w rites of the pre- 

 sumed translation of volcanic dust round half the equatorial 

 circumfeience of the eatth in six days as being in accordance 

 with our actual knowledge of these currents. There are 

 probably many readers of Nature besides my.^elf who would 

 be glad to be referred to the observations upon which this 

 staiement is founded. 



An opinion prevails that, in the rotation of the earth about its 

 axis, th.' higher parts of the atmosphere must to a certain extent 

 lag behind, thus producing an ea-.t wind relatively to the surface 

 of the earth ; and if we allow ourselves to adopt this view, we 

 may ea^ily imagine tliat in the equatorial regions there may 

 exist an upper current from the east having sufficient velocity to 

 meet the case supposed. But can thi, view be justified ? Is it 

 not more re isonable to consider that the whole of the earth's 

 atmosphere rotates with the earth as if it were part and parcel 

 of it ? It is difficult to see why it should not do so, unless we 

 suppose a resisting medium occupying the inter- planetary 

 spaces. 



It is certainly remarkable how well (on t'ne volcanic hypothesis) 

 the entire observations of the coloured sunsets and associated 

 phenomena agree with the supposition of an east wind sweeping 

 round the earth with hurricane speed in the upper regions of the 

 a'mosphere. Not only the obseri-ations from the Mauritius, 

 Cape Coast Castle, Brazil, and the West Inflies, but eve 1 those 

 from the Sandwich Islands and from Au-tralia, may be made to 

 harmonise with this theory, and the dust from Krakatoa may be 

 said to have made " a g rdle round the earth " in a fortnight. But 

 in case the theory should prove to be inadmis-ible, it may be 

 worth while to inquire v/hether some of these earlier observa- 

 tions may not find their exp'anation in an earlier eruption of the 

 same volcano. The first erup ion of Krakatoa is said to have 

 occurred on May 20, 'and it is evident that long before the 

 date of the great eruption (August 26) enormous quantities of 

 material had been ejected, vast fields of floating pumice having 

 been met with in the neiglibouring seas at various times between 

 July 9 and August 12. George F. Burder 



Clifton, Januat)' 7 



OiNE feature of the recent sunrises I have not seen described, 

 viz. a large and striking pink semicircle opposite the sun, 

 having a bluish centre. 1 have only twice seen it well marked, 

 viz. on November 27 and December 15. This seems to be one 

 distinct mark of difference between these sunrises and ordinary 

 ones, inasmuch as I never saw it before, though possibly this 

 may be partly owing to the phenomenon only lasting a few- 

 minutes at each time. On November 27 it was at its height at 

 7.4^ a.m. At 7.50 there was only a trace of it left. On 

 December 15 it was at its height at 8.6 a.m. At 8.4 it was 

 very faint, and by 8.16 it had again become so, and wa- whitish. 

 At 8.6 a.m. the north-western sky was darkish to an altitude of 

 about 5°, and light pinkish purple thence to lo" : so far the 

 appearance was quite ordinary ; but on the darkish sky rested 

 the broad half ring, which was pink, but the inner part inclining 

 to salmon-c-jloured. Being much brighter than the pinkish 

 purple, it ob-cured it where they crossed. I estimated the radius 

 of its outer edge at about 25°, and therefore ils apex was about 

 30° in altitude. Within the ring was a bluish-white semicircle 

 of about half the radius of the pink semicircle ; which was thus 

 12° or 13° in width. The sky beyond was blue. The pheno- 

 menon seemed to be an ordinary cirrus, though this w as of au 

 indefinite lype ; the spaces between its wisps were pretty blue in 

 all parts of the north-western sky, but partook somewhat of its 

 colour. On November 27 there did not appear to be any cirrus, 

 but the semicircle must have been on the film which has been so 

 remarkably coloured during sunrise and sunset. I have noticed 

 traces of this semicircle on one or two other mornings, but so faint 

 that I should not have noticed it if I had not looked for it. I 

 presume that it is of the same character as the pink circle 

 with green or blue centre that has been visible round the 

 sun by day. This al-o is a phenomenon which I never 

 ob-erved previous to last month ; it was most striking about 

 the 26th, but continues to be seen almost daily. This. 



