A^oz: I, 1883] 



NATURE 



car, retain impressions made upon them for a mo Jientary period 

 after the cause has ceased to act. If this snmiise is correct, then 

 the following would ensue. All musical tones bein^ produced 

 by vibrations striking upon the car in rapid succession, the first 

 vibration would continue to be felt during the strokes of a 

 number of succeeding vibrations. 



The secDud vibration coming upon the e.ir before the first 

 ceased to be felt would produce the effect of two in the time of 

 one, making the octave sound. 



The third would produce the effect of three in the time of 

 one, making the octave fifth ; the fourth, four in one, the double 

 octave; the fifth, five in one, the double octave third, and so on, 



tlie order exactly con'CsponJing -L'ltli that in -iihich the farlials 

 are heard. 



Of course while the successive strokes occur the first is be- 

 coming fainter in effect, and thus each partial in the above order 

 is heard with fainter intensity. 



What the first vibration is to the fecond and its successors 

 the second viliration is to the third and its successors, and thus 

 the series of partials is kept up as long as Ihe primary tone exists. 

 This also accounts for the strong partials heard in the rough 

 vibrations of the harmonium and the few partials heard from 

 the smooth tones of the flute. \\. C. Jones 



Chester, October 18 



The Green Sun 



On Sunday, September 9, the residents in Colombo, while 

 «njoying their evening stroll on Galle Face, were astonished by 

 a strange appearance in the heavens. The sky was cloudy, and 

 frequent squalls were passing over the sea, one of whicli just 



touclied Colombo. As soon as it was past, the sun emerged 

 from behind a cloud, of a bright green colour. It was then 

 about 10° above the visible horizon. The whole disk was dis- 

 tinctly seen, and the light was so subdued that one could look 

 steadily at it : indeed I should say its intensity was scarcely half 

 that of the full mion. The same phenomenon was also observed 

 on Monday and Tuesday. Wednesday was overcast, and X have 

 not heard of any observations being made ; and on Thursday 

 the sun had resumed its normal appearance. I was not in a 

 position to observ'C it in the morning ; but from reports from 

 other parts of the island I learn that the sun appeared green at 

 its rising, and afterwards changed to blue, like the flame ol 

 sulphur, giving little light till it b.id attained an altitude of about 

 20°, when it could no longer be watched with the naked eye. 

 Puling the day the light had a biuisli tinge ; and in the evening 

 the same phenomena were repeated in inverse order. The moon 

 also, to some extent, was affected in the same way. 



Can any of your correspondents give an explanation of this? 

 It has been suggested that a convulsion in the sun may have 

 given prominence to vapours emitting a green light ; but to me 

 it seems more probable that the cause is to be sought in the upper 

 strata of the earth's atmosphere. Can it have any connection 

 with the recent volcanic eruption in the .Straits of Sunda ? 



Colombo, September 19 W. 



In a clear sky, as the disk of the sun sinks down beneath the 

 horizontal line of the ocean, the parting ray is a brilliant emerald 

 tjreen. I have occasionally, but not often, had the pleasure of 

 seeing this interesting phenomenon, as the clear atmosphere has 

 to be accompanied with a cloudless regi m of the sky where the 

 sun is setting. The same effect is not produced by the sun set- 

 ting behind a distant bank of clouds. Probably the first ray 

 from the rising sun would be the same unexpected colour. 



Week St. Mary Rectory, Cornwall G. H. Hopkins 



Pons' Comet 



This comet already has a tail, though a very frint one. With 

 a 4i-inch refractor I traced it last night to a distance of 20' fron-. 

 the nucleus, at a position angle of about 75°. 



October 26 T. W. B.vciiHOUSF 



Earthquake 



Seeing in your last issue (vol. xxviii. p. 623) that Mr. Cecil 

 describes two distinct tremors of earthquake felt here by him, I 

 write to say that the same phenomena were experienced by 

 myself. I was disturbed in the night by what I mistook for an 

 alarum going off, but found that it was a glass on my water- 

 liottle viljrating violently. After a short pause the glass again 

 vibrated. I found next morning that I could exactly reproduce 

 this sound by shaking the washing-stand. I have never known 

 the washing stand to tremble before, even in a gale. 



H. Howard Crawley 



Pine View, Bournemouth, October 29 



STUDIES MADE OX THE SUMMIT OF THE 

 PIC DU MIDI WITH A VIEW TO THE 

 ESTABIISHMENT OF A PERMANENT AS- 

 TRONOMICAL STATION^ 

 TH.'\NKS to the indefatigable zeal of General dc 

 Nansouty and the engineer Vaussenat, a meteoro- 

 logical observatory has already been erected on the Pic 

 du Midi. After visiting the place with the Director of the 

 Higher Instruction on the occasion when this observatory 

 was handed over to the State, Admiral Mouchez came to 

 the conclusion that it might be possible to establish an un- 

 rivalled astronomical station on the summit, which is now 

 perfectly habitable. In the month of August last he 

 did us the honour of requesting us to study on the spot 

 the advantages and possible drawbacks attending an in- 

 stallation made under such e.xceptional conditions. The 

 details of our observations will form the subject of a 

 special memoir far too extended for insertion in the 

 Comples Rcndiis. For the present our remarks must 



I Note by MM. Thollon and TrerieJ, from Cowj-tcs Rmdm o' 

 October 15. 



