484 



NATURE 



[March 24, 1892 



Crustacea, by C. Warburton ; Arachnida and Myriopoda, 

 by R. Innes Pocock ; Insecta, by D. Sharp ; Echino- 

 dermata, by E. A. Minchin ; Vermes, by P. C. Mitchell ; 

 Coelenterata, by S. J. Hickson ; Spongiae, by E. A. 

 Minchin ; Protozoa, by C. Warburton. The utmost 

 pains have been taken to make the lists complete and 

 accurate, and to students of zoology they are practically 

 indispensable. In the introduction to Mammalia, Mr. 

 Lydekker notes that the number of new recent species is 

 extraordinarily large. He adds, however, that this is 

 "due to the elevation to specific rank of a host of North 

 American forms which would be regarded by most zoo- 

 logists as varieties." No fewer than forty of the " new 

 species" belong to this category. 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondent i. Neither can he undertake 

 to return, or to correspond with the writers of, refected 

 manuscripts intended for this or any other part of li m:vkv.. 

 No notice is taken of anonyvious communications. ^^ 



Sun Pillar. 



A REMARKABLY well-defined instance of this phenomenon 

 was seen by me at this place (460 feet above mean sea-level) 

 this afternoon. At 5.32 p.m. the sun was sinking behind a 

 thick layer of stratus cloud. There was a b;mk of dust haze, 

 so defined as almost to resemble cirrus, which apparently formed 

 a background to the clouds. When the phenomenon was first 

 noticed, about three-quarters of the sun's disk was below the 

 edge of the cloud bank ; and from ihe centre of that portion of 

 the disk visible there rose a tall column of brilliant light, ex- 

 ending upwards to about 5°, of the same width as the apparent 



I had noticed, a quarter of an hour previously, that the rays 

 of the sun, when behind a cloud, stood out in an unusually solid 

 and clearly defined manner. There was a good deal of anti- 

 cyclonic stratus (about 5000 feet) at the time, and the upper 

 part of the atmosphere was more hazy than is usual with a 

 north-east wind at this period of the year. At the earth's 

 surface the wind had dropped to an almost perfect calm, 



Lutterworth, March 5. Annie Ley. 



New Comet. 



The comet discovered here on the evening of Friday, March 

 18, is extremely small, though not very faint, and it has a 

 decided central condensation or nucleus. Its position at about 

 8h. 30m., March 18, was roughly determined as R.A. 341°, 

 Deck N. 59°. The comet was therefore situated in Cepheus, 

 and about 3° east-north-east of the star Delta in that constel- 

 lation. 



On March 19, at 8h., I reobserved the comet, and found its 

 rate and direction of motion to be 47' of arc east, and 12' north. 

 It will therefore shortly traverse Cassiopeia. 



The comet was discovered with a loinch reflecting telescope, 

 with eye-piece magnifying 40 times, and having a field of 65' 

 of arc. W. F. Denning. 



Bristol, March 21. 



[This is stated to be Winnecke's comet. — Ed.] 



First Visible Colour of Incandescent Iron. 



During the discussion which followed the reading of the 

 paper on " Colour Photometry" by Captain Abney and General 

 Fe^ting at the Royal Society on January 28, some interesting 

 remarks were made by Lord Rayleigh as to the colour exhibited 

 by heated iron when raised to such a temperature as only to be 

 just visible in a dark room. 



Lord Rayleigh stated that Weber, who, so far as I know, first 

 drew attention to this subject, described the first visible light as 

 a greenish-grey. Lord Rayleigh himself repeated the experi- 



Sun pillar ob.cr 



diameter of the sun, and narrowing almost to a point as it 

 touched the sun's rim. This convergence' became more marked 

 as the rest of the disk disappeared, until at the point at which 

 the latter was finally lost to sight the apex appeared to rest on the 

 edge of the cloud bank. The cone-shaped part at the base of 

 the pillar was the most luminous portion, and glowed with a bril- 

 liant orange-red tint, which gradually merged into the yellow- 

 white of the upper part of the column. The effect lasted for 

 some minutes after the sun's disappearance, but the pillar lost 

 its conical base and became less defined, while the clouds reced- 

 ing gave the appearance of the base of the pillar having risen in 

 the sky. 



NO. IT 69, VOL. 45] 



ment by making a piece of thin iron part ot the wall of a very 

 dark room, and heating the iron gradually by a Bunsen burner 

 upon the other side. Lord Rayleigh could not satisfy himself 

 as to the greenish tint, but was satisfied that no redness was 

 apparent. 



It struck me that a very convenient method of trying this ex- 

 periment would be to introduce a round bar of heated iron into 

 a thin sleeve, as shown in the annexed sketch, the sleeve being 

 closed with a cover lined with asbestos. In this way the heat 

 would slowly penetrate the sleeve, and the observers could note 

 the first appearance of visibility and the changes of colour that 

 followed. 



