Dec. 13 1883] 



NA TURE 



149 



to be about 320 metres per second. This is manifestly a mis- 

 print for 330 metres, but I should like to state that as far as my 

 experiments have gone the value for free air is not determined, 

 although 330'6, Regnault's value, is probably very nearly what 

 my method would make it. D. J. Blaikley 



103, Iverson Road, West Hanipstead, N.W. , December 10 



The Ophidian Genus " Simotes " 

 My attention has just been drawn to a note by Mr. H. O. 

 Forbes, published under the heading " The Genus Simotes of 

 .Snakes," in Nature, vol. xxviii. p. 539, in which he states that, 

 when describing a new species ai Simotes discovered by him in 

 Timor-Laut (P.Z.S. 1883) and which I observed was the first 

 of the genus known to occur eastward of Java, I overlooked 

 Krefft's Simot/s australis from Port Curtis, described in P.Z.S. 

 1864. It is a well known fact, pointed out by Dr. Giinlher in 

 1865 (Zool. Rcc. i.) and since admitted by Krefft himself (" The 

 Snakes of Australia "), that Simolcs australis is not a species of 

 that innocuous genus, but belongs to a widely different family of 

 poisonous snakes and to the genus Bracltyuropkis. 



London, December 5 G. A. BoULEXGER 



THE REMARKABLE SUNSETS 

 AX/E have received the following further communica 

 • • tions on this subject : — 



Having been rather too persistently of late requested 

 to explain both the why, and whence, and even the 

 future influences, of the recent very red and brilliant 

 sunsets, I gladly take the opportunity of addressing to 

 Nature the fen- remarks I have to make on the actual 

 facts and their proximate causes. 



In all truth the sunsets through the last week of 

 November and first four or five days of December have 

 been remarkably fine, and consecutively so numerous. 

 But each one, in so far as I have observed, was but an 

 intensification, and sometimes not much of that, of what- 

 ever goes to make up an ordinarily fine sunset, as custom- 

 ary to that season of the yeir and that direction of wind 

 with its concomitant kind of clouds. 



The season of the year not only causes the fiery show 

 to last longer than at many other times but enables it to 

 lake place while pedestrians are still engaged in their 

 constitutional afternoon walks in pleasant autumn tem- 

 perature, and before they shut themselves up for the 

 evening in their comfortable homes with artificial lights 

 around them. 



Some thirty years ago I used to spend every evening 

 month after month, at the ordinary dmner hour of others, 

 in the open air, watching for, and when seen making 

 quick coloured drawings of, any exceptionally fine sunset ; 

 taking in this way- three or four completely separate 

 pictures on the same evening between the time of the sun 

 vulgarly going down beneath the horizon, and at the last 

 the stars coming out in the darkness after the last vestige 

 of tviilight or high illuminated cirrus-cloud had dis- 

 appeared. 



In this manner I came to know practically that the 

 so-called after-glow, which has been alarming so many 

 persons within the last few days, whenever the temporary 

 disposition and arrangement of the clouds and vapour in 

 the air allow it to appear, is always more richly coloured 

 in reds of various kinds than any of the earlier glows and 

 more luminous splendours; and that the number of 

 modifications which any one sunset may go through, or 

 the number of different pictures it may make up, accord- 

 ing to changes in the clouds both above and below the 

 horizon, is bewildering. But the grandest effects, the 

 nearest approaches to the sublime, were always those when 

 the general light in the air was either so faint, or so 

 monochromatic, that the pigments in the colour box could 

 not be distinguished one from another without the aid of 

 artificial light. 



On December 3 and 4 of this week, on setting myself 



to watch and note with my former apparatus, I found all 

 these bizarre effects of colour and form in their old 

 intensity and their old kaleidoscopic quickness of change. 

 On the 3rd especially the reds were so powerful at certain 

 times, and the air so clear between me and them, that 

 the young crescent moon, though low down in the sky, 

 shone by contrast to the scarlet cloudlets around it with 

 a sort of supernatural lustre of blue silver ; while the gas- 

 lights under the same contrast, though in reality a gross 

 beery brown in colour, appeared of a delicate sulphur, 

 almost greenish, yellow. Those clouds, therefore, were 

 so red in consequence of something that had happened 

 to the sunlight illumining them which had not happened 

 to that illumining the moon. What was it then ? Simply 

 that the lower atmosphere of the earth was so particularly 

 clear of dust, haze, vapour, fogs, and positive obstructions 

 of lower clouds that the sun, though at the time a long 

 wa) below the horizon, was enabled to send its rays 

 through an unusual length of atmospheric path without 

 experiencing any other diminution than merely the 

 specific elimination of those particular rays in its spec- 

 trum-quiver to which the atmosphere, in that particular 

 condition, is antagonistic, leaving the field of glory to 

 others alone. 



Had the w-ind been ji:)«//;-west, the stoppage would 

 have been chiefly amongst and of the red rays of light, 

 where the black water-vapour lines are so numerous, 

 chiefly below D, near C, and especially about the region 

 of little '•''," which then becomes of giant size. But the 

 wind having been really nor//i-vie%l, the air was dry, 

 water-vapour lines practically absent, and, as Col. Don- 

 nelly most correctly remarked in this week's N.\ture (p. 

 132), the dry air band above D in the citron, and usually 

 called the low sun band in meteorological spectroscopy, 

 was at an immense maximum. Red light was therefore 

 practically unimpeded, green and blue much interfered 

 with, and more and more with every successive instant of 

 further descent of the sun below the horizon. So thus it 

 was that the spectroscope told at any instant through all 

 the varied displays that that coloured light so much ad- 

 mired was simply sunlight that had passed through an 

 extra length oi^ extra-dry air, and was being reflected at 

 the last from thin clouds at an extra height in the atmo- 

 sphere, where water-vapour is always at a minimum. 



But the sunset of December 5 was very different. In 

 the course of the evening there were two or three distinct 

 attempts, as it were, for the clouds to assume red hues, 

 but they lasted for only a few seconds each ; and though 

 some aspects of the scene were very fine pictorially, it 

 had to be chissedas a "yellow sunset." Next day showed 

 the cause of that in the wind below, as well as above, 

 turning round to east of north. December 6 and 7 had 

 poorer and poorer sunsets of both a yellow and sickly 

 type, and December 8 with a south-west wind has brought 

 in rain. 



Thus seems to have ;nded for the time this fine series 

 of Nature's evening p}rotechnic displays in the west (a 

 similar set having also been witnessed during the morn- 

 ings in the east) ; but demands are still made for an 

 explanation of why, and 10 what end? If we should 

 reply that, given a clear air, not too many clouds, and 

 these high up in the atmosphere and with surfaces well 

 constituted for reflection, the sunsets will always be fine; 

 and that they will be varied exceedingly in their beauty 

 even from moment to moment, according to the exquisite 

 manner in which clouds and cloudlets of cirrus streamers 

 form and dissolve and form again in all varieties of shape 

 and size and density, according to mere temperature 

 changes and other ordinary meteorological conditions of 

 the air; that is not enough to satisfy the present temper 

 of the public, who seem screwed up to a pitch of nervous 

 alarm that what they have been seeing, t ough to them 

 it has been like " music which gives delight and hurts 

 not," may yet have something to do with the green and 



