522 



NATURE 



[Oct. 18, 1877 



material melts down more rapidly in conseciuence of increased 

 temperature, then up to a certain point, at which guttering 

 begins, the rate of consumiition of the candle material will 

 increase. But in these experiments there was no guttering and 

 no smoking of the wick. C. TOMLINSON 



Ilighgate, October 13 



Selective Discrimination of Insects 



The remarks of Sir John Lubbock in a late lecture on the 

 relation of insects and (lowers leads to the inference that in his 

 opinion the brilliancy of colour rather than the odour is the 

 attraction. My observations lead me to suppose that it is not 

 the colour, but the particular odour of each variety or species of 

 flower which induces the visit. With great interest, not unmixed 

 with curiosity, I have observed (my attention was at first casually 

 excited) that bees particularly, and also butterflies, visit a distinct 

 variety and fur the time confine their attention to it, settling on 

 and sucking the honey of that variety only ; e.g., a bee settling 

 on a scarlet geranium will not go from it to another species or 

 variety, but gives its attention to the particular variety only, 

 irrespective of colour, whether scarlet, pink, or white, never 

 going from a s;arlet geranium to another scarlet flower, even if 

 in contact. Whatever the species of flower, it is the same — pelar- 

 goniums, petunias, heliotropes, lilies, &c. The visit is from 

 pelargonium to pelargonium, not from pelargonium to geranium 

 (both cranes bills), and from lily to lily, irrespective of colour. I 

 never remarked a bee go from a lily to an amaryllis, or the 

 reverse. The object of this distinctive selection appears to be 

 fertilisation. The indiscriminate admixture of the pollens of 

 distinct varieties would probably frustrate the ends of nature 

 and lead to monstrosities or barrenness. What would be 

 the effect of the admixture on its own stores is a distinct 

 question. So far as the insect is concerned, doubtless the 

 fact has relation to its own economy. Whatever be the 

 reason, there appears to be the harmonious adjustment of two 

 facts under the relations of one law. If the colour, and not the 

 odour, was the attraction, the visits would be indiscriminately 

 made to all flowers of a brilliant hue. The observation of the 

 lecturer as to flies being attracted by stinking plants or carrion 

 seems to prove the fact suggested. Flies settle indiscriminately 

 on all putrefactions, and will go immediately from a flower to 

 offal or from offal to a flower. With bees and butterflies there 

 is certainly a discriminative selection guided by odour ; I have 

 also remarked that some flowers are rarely, if ever, visited by 

 bees. 



I have never in the books I have read met with this observa- 

 tion, and when so acute and distinguished an observer as Sir 

 John Lubbock passes over the circumstance, I presume either the 

 fact has not been observed, or, if observed, has been considered 

 to be inconsequential. The observation may be worth nothing, 

 but in these days of viiimte scwticc, when every infinitesimal 

 variation is noticed and invested with importance, there may be 

 a significance in the fact which escapes me, but which, with 

 others, may have its value. So far as I know, the occurrence is 

 invariable ; being so, the inference is that odour, and not colour, 

 is the attraction. I have called the attention of others to the 

 occurrence, who have, watching the results, always come to the 

 same conclusion as myself. S. B. 



OUR ASTRONOMICAL COLUMN 

 The Nebula, Messier 8 (G.C. 4361).— Dr. Tempel 

 draws attention to the different appearance presented by 

 this large nebula at the present time from that depicted 

 in Sir J. Herschel's drawing made at the Cape of Good 

 Hope m 1836-37, which he considers can only be ex- 

 plained on the assumption of a shifting of the whole 

 nebula with respect to the stars by reference to which it 

 was delineated at the Cape, or by great changes in the 

 nebula itself. The case will be worthy of attention, 

 because it appears Sir J. Herschel's drawing was made 

 with much care, as he says " every attention has been 

 paid to exactness." The whole area occupied by the 

 nebula, so far as he could trace its convolutions, is stated 

 to be about one-fifth of a square degree. The relative 

 positions of the stars in and near it, to the number of 

 1S6, were ascertained by difl'erential observations with 

 9 Sagittarii ; " from these measures skeleton charts were 

 then constructed, and being divided into convenient tri- 



angles, the nebula was worked in upon them." A draw- 

 ing made under these circumstances might certainly be 

 expected to represent its actual features, and it appears 

 to be given with confidence by Sir J. Herschel. Dr. 

 TeiTipel, observing with the large Amici-telescope at 

 Arcetri, near Florence, finds that the reference stars 

 entered in the Cape drawing arc still as they then were, 

 with some insignificant variations of position or bright- 

 ness ; but the difference of the details of the nebula as 

 projected on these stars, from those shown by Sir J. 

 Herschel, are so marked as to leave, in Dr. Tempel's 

 opinion, no other explanation than is suggested above. 

 Prof. Schiaparelli, to whom Dr. Tempel had forwarded 

 his own delineation of the nebula for comparison with 

 that made at the Cape, remarks, after twice examining 

 it: — " Je dirai tout-de-suite, qu'il m'aurait c'td impossible 

 de reconnaitre la n<?buleuse avcc le seul dessin de J. 

 Herschel." The nebula is figured on Plate I. in the Cape 

 observations ; the description will be found at p. 14. 

 Probably Mr. EUery, who, as was stated last week, is still 

 occupied with new drawings of Sir J. Herschel's figured 

 nebula:, may be ab!e to express an authoritative opinion 

 with respect to the supposed changes in this object. 



The Binary Star n Centauri. — It appears from the 

 supplementary number of the Monthly Notices of the 

 Royal Astronomical Society that this star has not been 

 neglected during the critical portion of its orbit at the 

 observatory at Sydney. Mr. PI. C. Russell, the director, 

 publishes measures taken in each of the years 1870-77, 

 excepting 1S75, when he was in Europe, and expresses 

 his intention to observe it accurately during the next few 

 months, that the true time of the periastre, &c., may be 

 determined. The later measures indicate the necessity 

 of a correction for bias, the observer getting sensibly 

 differing angles of position according as the telescope was 

 east or west of the pier— in which, by the way, he is not 

 sinjjular ; the amount of the necessary correction was to 

 be investigated. It is very satisfactory to find that a 

 sufficient number of measures of this grand binary system, 

 for obtaining pretty good elements of its motion, are 

 likely to be put upon record at the present periastre. The 

 next we know will not occur until the middle of the 

 ensuing century. 



Jupiter's Satellites.— On October 8, M. Yvon 

 Villarceau laid before the Paris Academy of Sciences a 

 memoir, by M. Glasenapp, on the satellites of Jupiter 

 which appears to have been forwarded in competition for 

 the Fi IX Damoiscaii, and which had been found amongst 

 the papers of M. Lcverrier, one of the commission to 

 whom the adjudication of the prize had been referred. 

 It is known that M. Glasenapp has been occupied for 

 some time past at Pulkowa upon investigations connected 

 with these bodies. 



The Present Comets. — The comet discovered by 

 M. Coggia on September 14, though faint, is still well 

 situated for observation in the morning sky. The follow- 

 ing elements calculated by Herr E. Hartwig, from obser- 

 vations on September 14, 18, and October 6 have been 

 received from Prof. Winnecke : — 



Perihelion passage September I0'7566 M.T. at Berlin. 



Longitude of perihelion loS 10 57 ) M.Eq. 



,, ,, ascending node ... 251 3 52 j iS77'0. 



Inclination 77S1 6 



Log. perihelion distance o'i975o6 



Motion — retrograde. 

 Hence the following positions for Berlin midnight : — 



R.A. N.P.D. Distance from Di,-.lance from 



h. m. „ , the earth. the sun. 



Oct. 19 ... 7 39S ... 54 3 ... I 234 ... 1-662 

 „ 23 ... 7 2S-I ... 56 16 ... i-i66 ... i-6So 



„ 27 ... 7 14-9 ... 58 48 ... I"I02 ... I 699 



,, 31 ... 7 00 ... 61 42 ... 1'044 ... 1720 



Nov. 4 ... 6 43'S ... 65 3 ... 0-994 ... 1743 



„ S ... 6 256 ... 68 49 ... 0-953 ... 1-766 



