502 



NATURE 



\Oct. II, 1877 



It is now certain tliat Bialic, whilst at Wandesbeck, or Wan- 

 dcsburg, near Hamburg, sat to a painter, for here we have 

 evidence in a book published at Copenhagen, in 1668, that 

 King Frederick III. had that picture and that it was dated 

 Vandesbechi, 1597 ; and moreover, that that portrait had an 

 emblem upon it, which, from the motto, was presumably very 

 like that on mine, but the position and the words of the motto 

 differing, the motto ?ind also the inscription on King Frederick's 

 portrait being bdow the emblem, whilst on mine the motto is 

 on a ribbon or label wound round the pyramid, and the inscrip- 

 tion is on the other side of the picture. In King Frederick's 

 the emblem consisted of a pyramid with some kind of covering 

 ("sub pyrtmide tegumento quodam cooperta"), and so it is in 

 mine. That wind, tire, and water were also represented in that 

 emblem, as in mine, is clear from the words " ventus, ignis, et 

 unda " in tlie motto, which are precisely the words employed in 

 mine, the only difference in the two cases being that in the king's 

 there is the word " fremat," instead of " strepat " as on mine. In 

 my portrait the year 1597 is inferred from the inscription saying 

 "Anno 50 completo," Brahe being fifty years old on December 

 '3i 1 596. By a careful examination of Brahe's Latin Life by 

 Gas?endi, 1656, I found that Brahe wrote a remarkable poem 

 addressed to Ranzovius, in which the words '* e.xilium in patria " 

 occur ; and as he stayed at Kanzovius's from the end of October, 

 1597, I conjectured {Procadiiigs of Lit. and Phil. Soc. of Man- 

 chester, October 31, 1S76) that my portrait was painted between 

 that date and his next birth-day (December 13, 1597), a supposi- 

 tion confirmed by Herr Friis pointing out that the lost picture 

 of King Frederick's is dated at Wandesburg (Vandesbechi). 



That mine is no copy of that picture is manifest from the 

 diRerences which the notice in the " Inscriptiones Haffnienses " 

 has enabled me to point out. My conjecture is that Brahe sent 

 his portrait to King Frederick, who is expressly absolved by 

 Brahe from the blame of Brahe's expulsion from Denmark, and 

 that he advisedly wrote "pristine libertafi " instead of " hbertati 

 desiderata: " as on mine ; and further I have little doubt that the 

 same ar. ist painted both pictures. 



I have examined the portraits in the print room of the Biitish 

 Museum as well as the oil painting at the Royal Society, and 

 have taken much pains to ascertain the txi.stence of any other 

 portrait than mine representing Brahe later than 1587 ; ten years 

 earlier than mine. That it does not agree with the engraving 

 after Gumperlin's portrait is no proof whatever that mine is not 

 a good representation of him in his fifty-first year, when we con- 

 sider how much a man's features change in the ten years between 

 forty-one and fifty-one, and moreover Brahe may have been in 

 the meantime to the Promontory of Noses for a fresh one. But 

 whitever be the reasonableness of these conjectures, it is almost 

 certain that he sat twice at Wandesburgh to this portrait painter, 

 and that one of these portraits was considered worthy of a place 

 in the king's library. Samuel Crompto.n 



JManchcster 



Lumiere Cendree 



ScHROTER pointed out that it is towards the third day of the 

 new moon that the ashy light has the most intensity and that it 

 is stronger before the new moon than after. 



Schroter's explanation is that during the waning of the moon 

 the ashy light is stronger because the moon is enlightened by the 

 continents of Asia, Africa, and Europe, but after the new moon 

 by the Atlantic and Pacific Oceans. 



Godfray in his Astronomy says : — Supposing this difference to 

 exist, and this explanation to be the correct one, the phenomenon 

 must be just reversed in China and Japan. 



Has anything been done to test the accuracy of Schioler's 

 theory? If it is correct the ashy light cannot present the same 

 appearance to an astronomer in New York, because there would 

 be a greater proportion of reflecting surface in the hemisphere of 

 the earth turned towards the moon in the one case than the 

 other. 



Schrijter, I believe, found that the ashy light was stronger in 

 autumn than in spring. This cannot be accounted for by his 

 explanation, for the distribution of land and water remains the 

 same. 



I shall be obliged to any of your correspondents who can tell 

 me where there are any records of observations on this subject. 



B. G. Jenki.ns 



4, Buccleuch Road, Dulwich, October i 



Lightning Conductors 



In a paper on lightning conductors, communicated by us to 

 the Journal oi the Society of Telegraph Engineers, we gave at 

 full length our reasons for believing that the wire cage first 

 suggested some years ago, and recently proposed by Prof Clerk 

 Maxwell, as a protection against lightning, would not act as a 

 complete protection, since, although there is no resultant force 

 inside a closed conductor due to exterior statical electrification, 

 experiment shows the existence of such a force when electric 

 currents are passing either near or through a closed conductor. 

 The recent case of deaths by lightning in a mine, communicated 

 to the Asiatic Society of Bengal, on April 4 of this year, by J. 

 J. Whitty, Esq., superintendent of the Kurhurbari Collieries, 

 Giridhi, India, appears to add experimental proof to the reason- 

 ing advanced in our paper. Mr. Whitty says :—" The mine is 

 a shallow one, worked by levels driven on the side of a flat- 

 topped hill, only twenty feet from the surface, which is, 

 therefore, the thickness of rock above the coal-seam. The 

 working-face where the accident occurred is about 130 feet from 

 the opening. There were a number of miners in the drift at the 

 time. Those near the entrance were unaffected. The two who 

 were killed (a man and a woman) were at the working-face in 

 adjoining galleries, separated by about twelve feet of coal. A 

 young sal tree, standing as nearly as possible over the position of 

 the .accident, was slightly damaged, and in the ground at its base 

 a hole, about one inch in diameter, seemed to have been formed 

 by lightning. The little hill, or phteau, in which the mine is 

 situated is one of a small irregular group in the centre of the 

 coal field, about 200 feet high. It is formed of the coal-measure 

 sandstone. The dramage is thorough, and the mine was quite 

 dry. From the presence of the workmen the sides of the gal- 

 lery and the air in it were probably damper than the rock. The 

 tree or other vegetation on the hill is scanty. On the day of the 

 accident o'96 inches of rain fell." 



It would therefore appear that the two people who were killed 

 were practically entirely surrounded by a partial conductor in 

 connection with the earth. It will no doubt be objected that 

 twenty feet thickness of coal-measure sandstone, even when 

 damp on the surface, is not a good closed conductor, but we 

 think it is certainly as good a protection as would be afforded by 

 llie wires Prof. Clerk Maxwell proposes to lead merely along the 

 edges of a building. John Perry 



W. E. Ayrton 



The Imperial College of Engineering, Tokio, Japan, 

 August 6 



Electric Lighting 



I HAVE examined the patent (No. 10,919, November 4, 1845, 

 Edward Augustin King) which Prof. Mattieu Williams drew 

 attention to in Nature, vol. xvi. p. 459, as anticipating the 

 invention of Lodighin's electric wick, and I think LoJighin has 

 been clearly forestalled in principle, the practical details alone 

 being different in the two cases. 



I do not think, however, that Mr. King's patent includes 

 Koslofi's improvement, whatever value may attach to the latter. 

 I think it is very plain that porcelain is employed in King's 

 patent merely as an insuLating bar to connect the two forceps 

 rigidly together without shunting any of the current between 

 them past the carbon. J. MUNRO 



West Croydon, October 2 



Caterpillars 



Last year (Nature, vol. xv. p. 7) I communicated the result 

 of some experiments on the caterpillars of /■«■?•/,( /'ra.t.[/c<r from 

 which it appeared that, when these are artificially converted from 

 siiccincti into suspcttsi by cutting the loop before the exclusion of 

 the chrysalis, a certain number (a third or fourth of the whole 

 succeed in attaching themselves to the silk by the hooks in the 

 tail of the chrysalis in the manner of the true sicsfensi. I have 

 repeated the experiment this year with a like result, and I have 

 also had the satisfaction of witnessing the process of successful 

 exclusion, and comparing it with that of the chrysalis of Vanessa 

 nrticT. The method is essentially the same, except that the 

 rapid and assured precision with which the Vanessa chrysalis 

 thrusts up its tail and lays hold upon the silk, is replaced in 

 Pieris by long and laborious efforts, as if the tail were just a little 

 too short to reach the silk. 



I have likewise made similar experiments with another of the 



