Nov. 6, 1884] 



NA TURE 



BBStwi irthy — and proposes an instrument in which a weight drives 

 a clock-train furnished with a centrifugal speed-indicator. The 



il apparent weight of the driver caused by the earth's 

 up-and-down motion are to cause fluctuations in the speed of the 

 driven train, which are to he recorded in conjunction with the 

 time. The plan is, I think, new, but a less direct method of 

 measuring vertical movement could scarcely be imagined. The 

 fluctuations in speed will follow the changes of pull exerted by the. 

 driver with diminished implitude and retarded phase, andsuper- 

 posed on them there will be fluctuations following no rule, due 

 to inconstant friction and to mechanical imperfection of the train, 

 a^ well as the continuous acceleration which follows the starting 



chanism. To interpret the records would be altogether 

 Impracticable. 



.1 seismograph is a problem in applied dynamics 



5 of late years received a number of very satisfactory 

 solutions. Of instruments capable of determining earthquake 

 movements in absolute measure, and with reasonable exactness, 

 there is now no lack ; and it would be a pity if their wider employ- 

 ment were in any way retarded by the publication, on the au- 

 thority of Dr. Johnston-Lavis, of suggestions which may fairly 

 be said to lie outside the sphere of practical seismology. 



University College, Dundee, October 27 J. A. Ewing 



The Sky-Glows 



The description of the sky-glows as seen by Prof. A. S. 

 Herschel may justify an account of some seen near the Univer- 

 sity of Virginia, Virginia, during the past spring, from notes 

 made at that time. 



February 25. — For several days before this date there were 

 (if one may so call them) the normal glows at and after sunset. 

 On this day there was seen a single pink ray with well-defined 

 edges, about 4° broad, perpendicular to the western horizon, 

 reaching half way to. the zenith. 



March 24. — Ten minutes before sunset, the sun being behind 

 a small cloud, the bright oval "glare " in the west, which pre- 

 ceded nearly all the after-glows, was seen with its centre at an 

 elevation of 15 s (all these heights are rough estimates). It was 

 10° in diameter, and was surrounded by a band of a hazy red- 

 dish ashen colour (this band was usually seen with the "glare") 

 about 5° wide, which deepened in tint towards the horizon, and 

 there spread out on each side of the "glare" so as to form a 

 Somewhat triangular support for it. At 6.30 the sun set. No 

 colour had yet appeared on the eastern horizon. The "glare" 

 now seemed almost triangular in shape, with the deepest ashen 

 tints at the lower comers. As the sun de-cended, the " glare " 

 diminished in intensity from the apex of the triangle. At 6.35 

 1 ruddy colour on the eastern horizon, which spread 

 Dgular shape, apex upward, to a height of 25 to 30 , 

 and at 6.40 was an exact image of the "glare" in the west, 

 except that there were clear red tints instead of ashen, which 

 were deepest at the lower corners of the triangle. The colour 

 triangle then gradually rose from the eastern horizon, apparently 

 following the sun, till at 6.4S the pink tint appeared in the 

 western sky. increased in intensity, and was deepest at an ele- 

 vation of 60°. The colour in the east was now gone. (Several 

 attempts were made to observe the passage of colour across the 

 zenith, but in no case was there success.) The western horizon 

 was dazzling topaz-yellow, above the yellow pale blue, then 

 faint pink to the deepest pink. The pink gradually descended 

 toward the horizon, and when within 20° merged into the 

 ordinary sunset colour at 7.0. The general phases of the glow- 

 were as follows : — Triangular ashen haze with oval "glare " in 

 of triangle on the horizon at sunset. Ten minutes 

 later, triangular ruddiness in east, with base on the horizon, 

 jfnother ten minutes, pink in the west. Ten minute 

 colour disappears. This succession was also noticed on March 

 15. On March 4 the glow in the west reached its most intense 

 colour twenty minutes after sunset, but lasted twenty minutes, 

 disappearing forty minutes after sunset. 



On this evening (March 24) at 6.45, a cloud in the western 

 sky, there being then no pink there, at an elevation of 35 , was 

 coloured pale pea-green. This colour of the clouds floating at 

 an elevation of 35 was seen on other days, while the clouds 

 above and below retained their ordinary appearance. 



March 26. — After the same phenomena as detailed in the last, 

 even to the colour of the clouds, twenty minutes after the dis- 

 appearance of the first glows, at 7.20 there was a pale rose-glow 

 at an elevation from the western horizon of 30 to 35°, which 



reached almost to the Pleiades, of which six were then visible. 

 This second glow lasted about twenty minutes, and seemed to 

 descend to the horizon. It was almost identical with the first, 

 but fainter. 



March 29. — Same as preceding, without second after-glow ; 

 tints extended 6o° to 70 from horizon. 



These after-glows were noticed more or less during April, 

 July, and September, and here in Cambridge during this month 

 there have been several vivid displays. W. G. Brown 



Harvard College, Cambridge, Mass., 

 October 23 



I BEG to inclose you an extract from a letter lately received 

 by me from my cousin, Mr. Leeming, in the hope that it may 

 interest some of your readers. Ellen A. Day 



Greycoat Hospital, Westminster, October 24 



Extract from a Letter written by Thomas Leeming, Surgeon 

 ami Naturalist on Board tf.M.S. " Gulnare" on the 

 Admiralty Survey off Neiofoundland 



" Galtois, Hermitage Bay, Newfoundland, 

 September 12, 1 884 

 " There is one thing I have more than once forgotten to men- 

 tion to you, that is, an unusual appearance in the sky there has 

 been now for some months, which I think must be connected 

 with the red sunsets of last winter. In the finest weather the 

 sun has always about it a haze (not watery) extending some 20° 

 or 30°, white in the day-time, but as the sun nears the horizon 

 the sky has a pale salmon or ochrey tint. In the immediate 

 neighbourhood of the sun, the sky is of a vivid whiteness. 

 This appearance continues some time after sunset. I have 

 tried more than once to reproduce this effect, with water- 

 colours, but without success. Let me know if you have 

 observed or heard of anything of the same kind. I may also 

 mention that there has been until lately a great scarcity of 

 stars ; even on the fairest and darkest nights very few visible 

 under the third magnitude, and the Milky Way scarcely to be 

 seen at all. Things, however, are mending in this respect. " 



Peculiar Ice Forms 



Walking up from Chamounix to the Montanvert a fortnigh 

 ago, I came upon a form of ice which I think can hardly be o' 

 common occurrence, as I have not met with any description o 

 it, and have only once before seen it, and then also on the same 

 mountain side, and under similar conditions of season and 

 weather. 



The bank, which in this particul.u spot slopes it an angle of 

 about 45 = , and faces the north, is bare of vegetation for some 30 

 feet in depth, and 100 to 120 feet in length, the hillside above 

 being clothed with moss, ferns, and the usual undergrowth. 

 This bare slope was almost covered with a coating of ice nearly 

 four inches in depth, and of very curious structure, being formed 

 in four layers, the three upper layers each about an inch in 

 depth, and the lowest, which rested on the soil, being from five- 

 eighths to three-quarters of an inch. Each layer was composed 

 of an aggregation of filaments or elongated crystals, one-sixteenth 

 of an inch and downwards in diameter, and all of a length equal 

 to the thickness of the layer, ranged side by side like organ-pipes 

 or basaltic columns, and with pyramidal ends ; the bottom 

 points of one layer resting on the top points of the one below, 

 so that the layers could be easily detached one from the other. 

 The whole mass was pierced by vertical cylindrical cavities from 

 half to a quarter of an inch or less in diameter, and in most 

 cases penetrating from top to bottom, so that a pencil-case could 

 be dropped through endways. A horizontal section presented 

 somewhat the appearance of Gruyere cheese, minus the colour of 

 course, and with the solid part showing the crystalline form 

 described above. 



The mass had evidently been pushed up from below, because, 

 while the ice itself was perfectly white and colourless, it was 

 covered at the surface by a layer of dirt which might very likely 

 have concealed it from observation if it had not happened to be 

 broken. There was a good deal of snow higher up — nine inches 

 at the Montanvert — and the weather was fine, v. ith bright sunny 

 days and hard frost at night. This particular part of the bank 

 was in shade all day, and hardly thawed at all. I imagine that 

 the porous detritus forming the surface of the bank was under- 

 lain by hard rock (though it dRfnot occur to me at the time to 

 ascertain if it was so, and at whaFdepth), and that the water 



