Dec. 27, 1877] 



NATURE 



163 



After awhile, as the full daylight broke, it left (he smoky region 

 above and came down toward-; the deck, and I then discoverel 

 it to be neither bird nor bat, but a Fpecimen of the death's-head 

 moth, Sphinx Atrofos, whose flight 1 then witnes-ed tor the first 

 time. Af er runnii'g ihe gauntlet of several of the passengers, 

 who tried to caich it with their hats, it settled somewhere on 

 the spars or wo d'voik of the boat and escaped, ptrhaps to renew 

 its flight in a similar manner the following day. 



Hiyhfield, Gainsborough, December 21 F. M. BuRTON 



The Selective Discrimination of Insects 



May I be permitted to remark on Mr. Bridgman's com- 

 munication in Nature (vol. xvii. p. 102) ? He says he has 

 collected pollen grains of different kinds washed from the thigh 

 of an Andrena nigro-anca, and varying in col ur from orange-red 

 to white. The tiue inquiry as to the discrimination of insects 

 is not as to the colour on distinct kinds of pollen, but their homo- 

 geneity in respect of fertilisation. 



The remark I made implied, rather than expressed, that bees 

 and butterflies visited only those plants the admixture of the 

 pollens of which induced fertilisation. In this respect and in 

 this only, it appears to me, the investigation of the subject 

 becomes of importance. No fact of natural phenomena is with- 

 out use and without instruction ; there are no hap-hazards in 

 nature. If Mr. Bridgman, or other naturalists, can show the 

 admixture of the diveise grains of pollen collected by him from 

 the thighs of the creature named would not induce the fertilisation 

 of the plants from which they were collected, then the dis- 

 criminatory fact assumed is dispelled and the peculiarity observed 

 by Mr. Forbes and myself, and doubtless by others, becomes of 

 little value. The colour of the pollen grains is of no importance 

 in the inquiry, as observation shows ; the discriminatory facf, if 

 it has any importance, is not as to variations in colour, but the 

 collection of the pollen from distinct species of plants the admix- 

 tuie of which would not induce fertilisation. If it be proved that 

 the admixture of the collected \ oUens are only such as induce 

 fertilisation, then a natural phenomenon is disclosed of great im- 

 portance. This is the fact I imagine Sir John Lubbock meant 

 when he advised the pursuit of th- inquiry. 



I am still of opinion that it is odour, not colour, which is the 

 attractive element. It is so with carrion birds and the blow-flies 

 which collect on the foetid arum. In phenomena one particular 

 law appears to be repeated in all the natural kingdoms. The 

 same rule is also to be observed in physics. S. B. 



S unbury-on-Thames 



OUR ASTRONOMICAL COLUMN 



The Total Solar Eclipse of a.d. 418, July 19 — 

 Philostorgius, m his "Epitome of Ecclesiastical Histoiy," 

 relates that while Theodosius the Second was a youth, 

 on July 19, at the eighth hour of the day, the sun was so 

 greatly eclipsed that the stars were seen, and while the 

 sun was thus hidden there was seen in the sky a light in 

 the form of a cone, '* which some ignorant people called 

 a comet" ; and he goes on to describe the supposed dif- 

 ferences in the appearance of the phenomenon from that 

 of a comet, particularly remarking that it resembled the 

 flame of a torch, subsisting of itself, without any star to 

 serve as a base, and adding particulars of its track and 

 duration. That the object thus singularly discovered 

 during a total, or nearly total, eclipse of the sun, was 

 really a comet as the ''ignorant people" supposed, is 

 proved by the records in the Chinese Annals. The eclipse 

 to which reference is made by Philostorgius look place on 

 July 19, A.D. 418. The comet of that year is stated in 

 Pingr^'s Cometos^raphie to have betn discovered in the 

 10th moon, commencing November 15, in which he fol- 

 lows the Jesuit, Couplet, but the account given by Mr. 

 Williams, on the authority of the She Ke and Ma Twan 

 Lin, dates the appearance of the comet on day Kang 

 Tsze of the 5th moon, when it was situate in Ursa Major; 

 on September 15 it was on the confines of Leo and 

 Virgo ; " it was bright, and gradually lengthened until it 

 was 100 cubits in length." Philostorgius also refers to 

 the passage of the comet through Ursa Major, and says 

 it continued visible until the end of the autumn. 



It may interest some readers to have particulars of the 



eclipse, during which it is recorded that a large comet was 

 first discovered. The following figures depend upon a 

 very similar system of calculation to that applied to other 

 ancient eclipses, described in this column : — 

 G.M.T. of Conjunction in R. A. 418, July 18, at 23h, 3m. 17s. 



Right Ascension ... 



Moon's hourly motion in R. A. . . . 



Sun's ,, „ „ ... 



Moon's declination 



Sun's ,, 



Moon's hourly motion in decl. . . . 



Sun's „ „ „ ... 



Moon's horizontal parallax 



Sun's „ „ 



Moon's true semi- diameter 



Sun's „ .. 



.. 118 30 48 

 38 34 



2 32 

 21 23 10 N. 

 21 2 41 N. 



3 40 S. 

 028 S. 



59 38 

 09 

 16 15 



1548 



At Constantinople these elements give a very large 

 eclipse, commencing at oh. 5 m. and ending at 2h. som. 

 local mean time, magnitude, 0-95 ; at a short distance to 

 the south the eclipse would be total. 



Variable Stars. — The following are geocentric 

 minima of Algol and S. Cancri during the ensuing two 

 months, so far as they are visible in this country. They 

 are expressed in Greenwich mean time, and are calculated 

 from Prof. Schonfeld's elements : — 



ALGOL 

 h. HI 



12 29 Jan. 

 9 18 Feb. 



6 7 

 17 23 



14 13 

 XI 2 



7 52 



S. CANCRI 

 h. m. I 

 10 20 j Feb. 



9 35 I „ 



Astronomical Phenomena in 1878.— The principal 

 astronomical occurrence of the next year is the total lolar 

 eclipse of July 29, which traverses British Columbia and 

 the United States ; the American astronomers will doubt- 

 less give a good account of it, au'i it is reponed they are 

 likely to have coadjutors from this side of the Atlantic. 

 There will be a transit of the planet Mercury on May 6, 

 Visible in this country to pa^t the time of the nearest 

 approach of centres, and a lunar eclipse on August 12, 

 magnitude o'6, wholly visible here. Mars will be occulted 

 by the moon on the evening of June 3, and the second- 

 magnitude star o- Sagittarii on the afternoon of October 

 30 ; on November 10 the moon traverses the Pleiades. A 

 return of Encke's comet to perihelion also takes place in 

 the summer, but not under favourable circumstances for 

 observation, and the comet of short period detectt d by 

 Tempel on July 3, 1873, will again arrive at perihelion 

 late in the spring. Saturn's rings disappear on February 

 6, but reappear on March i, according to BeSiel's 

 elements. 



FERTILISATION OF GLOSSOSTIGMA 

 'HP HE following letter to Mr. Darwin has been forwarded 

 ■'• to us by him for publication : — 



" Museum, Auckland, October 23, 1877 

 " My Dear Sir, — I forward to you a copy of a paper on 

 the fertilisation of Selliera, one of the Gooaeniacea, which 

 perhaps you may care to glance over. When I wrote it 

 I did not know of your notes on Leschenauliia^ published 

 in the Gardener's Chronicle for 187 1. In both plants the 

 pollen is shed before the expansion of the flower, and 

 neatly collected in the indusium, but in Selliera the 

 stigma is situated within the indusium, and by its gradual 

 upward growth after the flower expands slowly forces out 

 the pollen, which is then transferred by insects to older 



