August 1, 1898.] 



KNOWLEDGE. 



183 



To the Editors of Knowledge. 



Sirs, — Colonel Markwick, in his interesting paper on 

 variable stars, is at pains to reconcile bis flat curves at 

 minimum with tbe real ones. This would be easily ex- 

 plained by supposing the nearer star imt to pass centrally 

 over the other, but so that its upper or lower edge 

 coincided or overlapped its primary. Then the slightest 

 movement to left or right would reduce the occulting area. 

 It would be interesting to calculate curves for bodies of 

 equal size, but only partially occulting one another. 



The whole subject suggests in the future a wonderful 

 widening of the harvest of fact. Harold Whichello. 



HOOKED PROCESS ON BEES' MANDIBLES. 

 To the Editors of Kno^nxedge. 

 Sirs, — In Knowxedge, October, 1895, appeared a letter 

 and sketch of a hooked process on the mandible of the bee 

 {Apis melirica). In the succeeding number, Mr. T. A. 

 Cowan wrote asserting that they were not hooks, but hairs, 

 and pointing out that they were correctly figured in his 

 book on the honey bee. This is rather ancient history, 

 but my excuse for referring to the subject after so long an 

 interval is that immediately after the publication of my 

 letter I was laid on my back by a long illness, which for 

 a long time after recovery prevented the use of my micro- 

 scope. I have now taken up the subject again. I have 

 asked the opinion of several gentlemen of authority as 

 entomologists — among others, Mr. Fred. Enock, whose most 

 interesting papers are now appearing in your columns — and 

 they endorse my view that the objects imder discussion 

 are hooks and not hairs. I have carefully examined 

 Mr. Cowan's book, and I find that they are not liijiircd there, 

 neither is any reference made to them, inclining me and 

 others to think that Mr. Cowan has mistaken the hairs 

 that fringe the mandible for the hooks that are placed on 

 the buttress of chitine that bridges the concavity of the 

 mandible. They are so specialized that Mr. Enock says 

 that they must have some very practical use (I suggested 

 in my letter that they might be used in clustering), but at 

 present that use is a mystery. Sir John Lubbock was 

 kind enough to inform me that he had not previously 

 noticed them, and had no idea of their utility ; so that 

 perhaps I may, though with the humbleness of the tyro, be 

 permitted to claim that I was the first to call attention to 

 these interesting microscopic objects, all the more remark- 

 able for having remained so long unnoticed on an insect 

 so closely studied as the hive bee. Walter Wesche. 



ARTIFICIAL FACUL^. 



By the Rev. Arthur East. 



AN article appeared in the December and April 

 Numbers of Knowledge giving an account of some 

 experiments made with paper pulp in order to 

 illustrate a theory of the formation of sunspots. 

 It is proposed in the present article to apply the 

 same method to faculie. 



It had long been almost necessarily supposed that the 

 facul», as the bright rifts and ridges seen on the edge of 

 the sun are called, extended really over the whole spot- 

 zone surface of the sun ; but it was reserved for Prof. Hale 

 actually to photograph them with his spectro-heliograph 

 in localities extending across the whole disc, where, tele- 

 scopically, faculse are invisible. 



A delightful account of this triumph of photography is 

 given in Sir Robert Ball's " Story of the Sun"; and by the 

 kindness of Prof. Hale, now at the Yerkes Observatory, 



I am enabled to illustrate this article with three of the 

 remarkable pictures of the solar surface taken with the 

 spectro-heliograph of the Kenwood Observatory in Chicago. 



What will immediately strike anyone accustomed only 

 to the telescopic appearance of spots is the chiudij aspect of 

 the solar surface, and the absence of the clearly cut, crisp 

 outline of the spots to which he is accustomed, but an 

 aspect which the artificial spots (as may be seen) very 

 faithfully reproduce ; this cloudy appearance is not due, I 

 believe, to any imperfection of the photograph, but to the 

 faoulic being so much more evident. We seem to see here 

 cloudy masses of vast extent lifted high above the surface 

 of the photosphere, and bright because lifted beyond the 

 " fog or smoke stratum " of the sun (an expression of Prof. 

 Hastings, endorsed by Prof. Young, and most consoling to 

 the Londoner). 



There is one most instructive feature in the spectro- 

 heliographs here given, viz., that there are several pairs 

 of spots visible — not circular, but elliptical, and with the 

 appearance of being, as it were, bafk to hack, as if the spots 

 were openings on opposite flanks of a vast tumulus ; and 

 looking as though, were the overlying mass to be removed, 

 a single orifice would be disclosed underneath. 



And it also very clearly appears from these pairs of spots 

 that the penumbra being widest on the eastern edge of a 

 spot which is passing off the limb, is no argument against 

 the Wilsonian theory of depression, but may be due to 

 the spot being crateriform, or an elevated depression, as 

 suggested in a former article. 



Now, this lifting of the photosphere into facul* is pre- 

 cisely what we frequently get with the artificial spots, as 

 Fig. B may help to show. When the heat is applied, often, 

 instead of any spot appearing, flooculent masses rise, and 

 are, moreover, remarkably permanent — a characteristic 

 feature of faculm according to Prof. Young : the heated 

 water meanwhile escapes at the sides of the upheaved 

 mass ; but, if the mass be removed, an ordinary spot is 

 found below (Figs. A and C). 



There is probably no doubt now remaining that faculfe 

 are very closely related to spots ; spots are apparently 

 always accompanied by facuhp, although faculse often occur 

 without spots, but the particular nature of the relationship 

 is not known. 



The behaviour of artificial faculas — as Figs. A, B, and C 

 wiU show — ^suggests that the faculse are really masses of 

 condensed vapour which ovirhawj ami conceal the spots, and 

 that in many cases, if not in most, if the faculm are 

 dispersed an ordinary spot will be disclosed. Thus Fig. A 

 shows two patches of faculae, but one is uncovered to 

 show the spot below ; Fig. B, again, is a larger mass of 

 artificial facuh^. After this photograph was taken, the 

 overhanging mass was gently removed in one place, and 

 Fig. C was taken, to show the ordinary spot below. The 

 relationship between facuLe and spots would thus be 

 exceedingly close, the suggestion being that wherever 

 faculfe are seen there also are corresponding spots below, 

 from which the vapours forming the faculre are being, or 

 have been, ejected ; that in certain conditions of the solar 

 atmosphere, as in our terrestrial atmosphere, these con- 

 densed vapours are reabsorbed or dispersed, and the open 

 spot (if it may be so termed) disclosed ; but that at other 

 times the vapours are not so dispersed, and continue to 

 overhang the spot from which they come, entirely con- 

 cealing it, and appearing as part of the photosphere, except 

 to the eye of the spectro-heliograph. 



If this be so, and facul;^ in all cases have spots below 

 them, it would explain very simply the extreme rapidity 

 with which large spots at times appear ; they are, in fact, 

 uncovered. The telescope shows, perhaps, a disc entirely 



