NATURE 



17 an. 3, 1884 



In such weather as we had the ascent of Ben Nevis is 

 decidedly more pleasant and less fatiguing than in 

 summer. It is well, however, to warn the readers of 

 Nature that our case was exceptional, and that under 

 adverse circumstances such an enterprise is likely to be 

 both unpleasant and dangerous. G. Chrvstal 



I 



THE REMARKABLE SUXSETS 

 'NFORMATION with regard to these beautiful pheno- 

 • mena and their cause is rapidly being collected, and 

 at the same time the opinions of those who have given 

 most attention to them are being stated, both here and on 

 the Continent. Among the latter we may refer to a me- 

 moir presented by Prof. Forel to the Societe \'audoise 

 des Sciences Naturelles, on the 19th of December. At 

 the beginning of the displays in Switzerland, M. Forel 

 ascribed them to those causes which produce the ordinary 

 after-glow so beautifully visible in mountainous countries, 

 and at first he considered that the meteorological conditions 

 were such as to favour this view. Further inquiry, however, 

 he now states has made this hypothesis absolutely unten- 

 able. One of his arguments is that the glows which first 

 appeared in November and then decreased to 3rd Decem- 

 ber, regained a maximum on the 24th and 25th. Now 

 from the 22nd to 26th December, Switzerland was the 

 centre of a maximum of atmospheric pressure, the 

 barometer being higher there than in any of the surround- 

 ing countries. Exactly the opposite held in November, and 

 this confirms him in the idea that meteorological factors 

 alone do not suffice to explain the glows. He also 

 describes the dates and tracts of the chromatic pheno- 

 mena observed, and considers that their origination in 

 Krakatoa is a simple and sufficient explanation. La 

 Nature for the 29th ult. contains an interesting com- 

 munication from AI. Van Sandick, an Engineer des 

 Fonts et Chaus~des, at Pedang, who was an eye witness 

 of the later stage of the eruption. He was on 

 board the Govcnior-General Loudin, and was close to 

 Krakatoa on August 26th. His communication is ac- 

 companied by a very detailed map, showing the changes 

 which have supervened not only in the Straits themselves, 

 but also on the neighbouring coasts of Java and Sumatra, 

 but we shall return to this important letter. 



The new observatory on the summit of Ben Nevis has 

 been utilised for the collection of snow, with a view of 

 determining whether or not it contains any dust particles. 

 This has been forwarded to Mr. John Murray of the 

 tViffZ/Vv/ivr Commission by Mr. Omond the superintendent 

 of the obser\-ator)-. We may hope to hear soon whether 

 the results are positive or negative on this special point of 

 inquiry. Wc have to call attention to the important letter 

 of Mr. Macpherson published below. We learn from the 

 \\'cekly British Colonist, published at Victoria, British 

 Columbia, that the sunsets made their appearance there 

 on November 27th. Long after sunset the light in the 

 sky became more fervent in colour, till at last the waters 

 in the harbour and straits borrowed the splendid crimson. 

 Darting and rapidly moving blood-red rays of light were 

 seen shooting far into the sky, suggesting an aurora. A 

 letter from St. Raphael, on the shores of the bay of San 

 Francisco, dated December 4th, refers to the magnificent 

 sunrises and sunsets. The date of their commencement 

 is not stated. From Kiakhta, on the Mongolian frontier, 

 we learn that the glows there began on December nth, 

 and terminated on the 25th. 



The glows were seen some time before November 6th 

 at Kalim Pong, twenty miles north-west of Darjeeling. 



We have received the following further communications 

 on this subject : — 



The body of evidence now brought in from all parts of 

 the world must, I think, by this time have convinced Mr. 

 Piazzi Smyth that the late sunrises and sunsets do need 



some explanation, more particular than he was willing to 

 give them. With your leave I should like to point out 

 from my own observations and those of others that, 

 " given a clear sky " and the other conditions put by Mr. 

 Smyth, the sunrises and sunsets of other days, however 

 bright and beautiful, have 710I given anv such effects as 

 were witnessed, to take an instance, here on Sunday 

 night, December i6th. I shall speak chiefly of the 

 sunsets. 



(l.) These sunsets differ from others, first in their time 

 and their place or quarter. Sunset proper is, I suppose, 

 the few minutes between the first dipping and the last 

 disappearance of the sun's disk below the true horizen ; the 

 pageant or phenomena we call sunset, however, includes 

 a great deal that goes on before and after this. The re- 

 markable and specific features of the late sunsets have 

 not been before or at sunset proper : they have been 

 after-glows, and have lasted long, very long, after. To 

 take instances from your number of the'l3th ult., Mr. F. A. 

 R. Russell notices that on November 2Sth, the sun having 

 set at 3.55, one after-glow lasted till 5.10, and was then 

 succeeded by another " reaching high above the horizon." 

 The day before he mentions the after-glow as lasting to 

 5.20. On the 29th a " foreglow " is reported as seen in 

 London from 5.30 to 7.30, that is more than two hours 

 before sunrise, which was at 7.43. On December ist, 

 sunset being at 3.53, Mr. Russell observed an after-glow 

 till 5.35 ; on December 4th the first dawn at 6.5, the sun 

 rising at 7.50 ; the next day dawn at the same time, sun- 

 rise 7.51 ; that evening, sunset being at 3.50, he observed 

 not a glow only but " spokes of rays from the glowing 

 bank " at 4.45, thatis to say, sunbeams, visible in the shape 

 of sunbeams, 55 minutes after sunset. Mr. Johnston- 

 Lavis speaks of the after-glow at Naples as at a 

 maximum an hour after sunset Here at Stonyhurst on 

 December i6th, the sun having set at 3.49, the glow was 

 observed till 5.50. Now winter dawns and after-glows do 

 not last from an hour to two hours, and still less so day 

 after day, as these have done. The recent sunrises and 

 sunsets then differ from others in duration. 



They differ also in the quarter of the heavens where 

 they are seen. The after-glows are not low lingering slips 

 of light skirting the horizon, but high up in the sky, 

 sometimes in the zenith. 



I have further remarked that the deepest of the after- 

 glow is in the south, whereas the sun below the horizon is 

 then northing. I see that other observers take notice of 

 the same. 



(2) They differ in their periodic action or behaviour. 

 The flushes of crimson and other colours after ordinary 

 sunsets are irregular, not the same nor at the same time 

 for two days together ; for they depend upon the acci- 

 dental shapes and sizes and densities of the cloud-banks 

 or vapour-banks the sun is entering or freeing himself 

 from, which vary and can never be alike from day to day. 

 But these glows or flushes are noticed to be periodic 

 before sunrise and after sunset. Mr. Russell furnishes 

 exact estimates of the intervals of time, which he finds to 

 be the same day after day. 



(3) They differ in the nature of the glo-dj, which is both 

 intense and lustreless, and that both in the sky and on the 

 earth. The glow is intense, this is what strikes every 

 one ; it has prolonged the daylight, and optically changed 

 the season ; it bathes the whole sky, it is' mistaken for 

 the reflection of a great fire ; at the sundown itself and 

 southwards from that on December 4, 1 took a note of it as 

 more like inflamed flesh than the lucid reds of ordinary 

 sunsets. On the same evening the fields facing west 

 glowed as if overlaid with yellow wax. 



But it is also lustreless. A bright sunset lines the 

 clouds so that their brims look like gold, brass, bronze, or 

 steel. It fetches out those dazzling flecks and spangles 

 which people call fish-scales. It gives to a mackerel or 

 dappled cloudrack the appearance of quilted crimson 



