November 24, 1692 J 



NATURE 



77 



LETTERS TO THE EDITOR. 



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

 pressed by his correspondents. Neither can he undertake 

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

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communiccUions.\ 



The New Comet. 



The comet discovered by Mr. Holmes on November 6 was 

 observed here on November 9 at 5h, 50m., and found to consist of 

 a very bright circular nebu osity with central condensation. The 

 diameter of the comet was 5' 41". 



It was re observed on November i6at loh. 45m.,andits physical 

 appearance seemed to have undergone a complete transformation. 

 The diameter had increased to 10' 33", and thecometary material 

 had become much fainter and more irregular. The nucleus was 

 now in the form of a bright streak, and this was enveloped in a 

 large famt coma. A small star was seen just N. of the W. 

 extremity of the nucleus, and the latter seemed composed of 

 knots of nebulosity. 



S 



Nov. 9, sh. 50m. 



Nov. 16, loh. 45m. 



On November 19, I4h, 15m., the comet was seen again. Its 

 general aspect was much fainter, and it exhibited a further in- 

 crease in dimensions. I carefully determined its diameter as 

 14' 30", but the outlying portions were very tenuous and in- 

 definite. 



From Berberich's elements given in Edinburgh circular No. 

 33, it appears that the comet is moving rapidly away from the 

 earth. The great increase in its apparent diameter is therefore 

 not a little remarkable. On November 9 the comet was about 

 203 millions of miles distant from the earth, and its real diameter 

 must have been 333,000 miles. On the i6fh this had increased 

 to 652,000 miles. By the 19th the comet's distance had become 

 217 millions of miles, and its real diameter 925,000. In ten days, 

 therefore, the cometary material expanded nearly threefold. 



Bristol, November 20. W. F. Denning. 



The Light of Planets. 



A FEW facts relative to this subject may be interesting. At 

 Plymouth on August 12, about 9 o'clock, favoured with a beauti- 

 fully clear horizon, the brilliancy of Mars was so great that it 

 cast a distinctly bl ick shadow on a piece of white paper from an 

 ordinary walking stick held at a distance of 4^ inches ; the out- 

 line of the hand, under the same conditions, was also easily per- 

 ceptible. A faint, yet decided, darkening of the white cliffs of 

 the shore was caused by a person standing upright — the slope 

 being about 45°. The point of observation was at the extreme 

 north-west of the Sound, and the splendour of the planet's light 

 reflected from three or four miles of water is perhaps unrivalled. 



The light of Jupiter has often enabled me, when u-^ing the 

 telescope at a southern window, to make drawings and such 

 references to books, &c., as were found necessary, without any 

 other illumination. John Garstang. 



Springwell House, Blackburn, November 21. 



Rutherfurd Measures of Stars about ^ Cygni. 

 In order to prevent any possible misapprehension in connection 

 with your notice (Nature, vol. xlvi. p. 619) of Mr. Rutherfurd's 

 measures of the stars surrounding 3 Cygni, may I call attention 

 to the following ? — The two stars of Argelander, 27.3435 and 

 28.334 , concerning which a doubt is expressed in my papei, 



NO. 1204, VOL. J 7] 



are certainly lacking on the Rutherfurd plates. If they were 

 present they would be very near the edges of the plates, and it 

 is for this reason that I doubted whether we should expect to 

 find them at all. The star numbered 28 in the Rutherfurd list, 

 which appeared only as a sort of elongation of No. 27 on a plate 

 taken at this Observatory, April 19, 1892, is one of the com- 

 ponents of 22539, as was pointed out by Mr. Burnham in the 

 Astronomical Journal, No. 268, and by myself in the same 

 journal. No. 266. Harold Jacoby. 



Columbia College Observatory, New York, 

 November 11. 



The Alleged " Aggressive Mimicry" of Volucellce. 



Mr. Poulton's letter calls for few words in reply. I invited 

 Mr. Poulton to produce observations in support of his state- 

 ment that the two varieties of Volucella bombylans lay in the 

 nests of the bees which they respectively resemble. To this 

 invitation Mr. Poulton has not responded. He tells us that his 

 account represented "a very general impression"; that the 

 same impression has been set forth in a showcase at the Museum 

 of the Royal College of Surgeons ; that even if he were mis- 

 taken it was well, if through his mistake the truth shall the 

 more abound. It is thus admitted that in making that statement 

 Mr. Poulton relied not on original authorities, but on the 

 general impressions of others. That these impressions are 

 in any sense correct there is as yet no evidence to show. 



Compared with this, Mr. Poulton's error as to Bombus 

 muscorum is of course comparatively trifling and it would be 

 useless to pursue the matter, were it not for discoveries made 

 in the process of unravelling it. 



I pointed out that V. bombylans is common in nests of B. 

 muscorum, a bee which it does not resemble. Mr. Poulton in 

 reply maintains the opinion that V. bombylans var. mystacea 

 does resemble B. muscorum. In defence of this statement he 

 refers to (i) the showcase at the Royal College of Surgeons, 

 where the resemblance is set forth ; (2) a recent book, " Animal 

 Intelligence," by Mr. Lloyd Morgan, where the resemblance 

 is again asserted and illustrated by figures of insects in the 

 similar showcase at the Natural History Museum. 



In following up these clues I came to unexpected results, 

 (i) There is a', the College of Surgeons a showcase, as stated, 

 illustrating the likeness of Volucella to humble-bees. The 

 label states that "the resemblance enables them [the flies] to 

 escape detection." Two bees are exhibited bearing a good like- 

 ness to the var. mystacea, and, as Mr. Poulton says, they are 

 labelled " j5. muscorum." The one, however, is a worker of 

 B. sylvarum L., and the other is probably a male of the same 

 species. Neither can be mistaken for B. muscorum, which they 

 do not resemble. 



(2) At the Natural History Museum bees of several species 

 are shown beside the Vohccelhc, with a similar statement that 

 the resemblance enables the flies "to enter the nest of the bee 

 without molestation." Not one of these bees is B. muscorum, 

 nor are any of them said to belong to this species, for no names 

 are given. Nevertheless, on turning to Mr. Lloyd Morgan's 

 book, which I had not before seen, I find the statement (p. 90) 

 that V. bombylans "closely resembles" B. muscorum, the 

 passage continuing in the words of the Natural History Museum 

 label. Figures are added showing the two forms of V. bombylans 

 and two very different bees, both marked '' B. muscorum.'' 

 Now the figures are from photographs of certain specimens in 

 the showcase, and on reference to the specimens in question, it 

 appears that one of them is a yellow-banded humble-bee (per- 

 haps B. hortorum), while the other is one of the red -tailed 

 humble-bees! These two are put out to match V. bombylans 

 and the var. mystacea respectively, and of course have no like- 

 ness either to each other, or to B. muscorum, though both are 

 referred to this species by Mr. Lloyd Morgan. 



Mr. Poulton's choice of B. muscorum as a form resembled 

 by the var. .wjj/ar^a probably therefore arose from the wrong 

 naming at the Royal College of Surgeons. How Mr. Lloyd 

 Morgan came to call the two different bees by the name B. mus- 

 corum, which belongs to neither, I cannot tell. Perlfaps this is 

 in part an echo of Mr. Poulton's previous mistake. 



Any one by reference to a collection of bees may easily 

 satisfy himself that the common and ordinary B. muscorum, 

 with its bright brown thorax, does not resemble V. bombylans, 

 though this fly is common in its nests, just as V. pellucens li\es 

 in wasps' nests, though it does not resemble a wasp. 



In the absence of direct evidence in its favour, and inasmuch 



