Nov. 15, 1888] 



NATURE 



hi 



My "segregate fecundity" and ^Tr. Romanes's "physio- 

 logical selection " are the same principle ; and our theories still 

 further correspond in that we both insist on the prevention of 

 intercrossing cs a necessary condition for divergent evolution. 

 This conclusion was reached by me through investigations made 

 many years ago, and was maintained in my paper on " Diveisity 

 of Evolution under One Set of External Conditions," and in 

 still stronger language in articles in the Chrysanthemum. (Yoko- 

 hama), January 1883, and in the Chinese Recorder (Shanghai), 

 July 1885. In the first of these papers I used the word 

 "separation " to indicate the phase of the principle that results 

 from migration ; but for a fuller discussion of the subject I found 

 it necessary to introduce " segregation " as the more significant 

 term ; and in the second paper I maintain that " While external 

 conditions have power to winnow out whatever forms are least 

 fitted to survive, there will usually remain a number of varieties 

 equally fitted to survive ; and that, through the law of segregation 



constantly operating these varieties continue to diverge 



till separate species are fully established, though the conditions 

 are the same throughout the whole area occupied by the diverging 

 forms ; " and in the third paper I said, " I am prepared to show 

 that there is a law of segregation rising out of the very nature 

 of organic activities, bringing together those similarly endowed," 

 and causing "the division of the survivors of one stock, occupy- 

 ing one country, into forms differing more and more widely from 

 each other." Since then, my nomenclature of the subject has 

 been worked out with that word as the central symbol of my 

 theory. It is therefore a pleasure to find that Mr, Romanes uses 

 the same word to express the same general idea, giving to his 

 theory the alternate name of "segregation of the fit" (Linnean 

 Society's Journ.—Zool., vol. xix. pp. 354,395), and in one place at 

 least describing it as "physiological segregation" (see letter on 

 "Physiological Selection," Nature, vol. xxxiv. p. 408). 



As I have explained in chapter iv., I at first thought of using 

 " physiological segregation " in place of "industrial segregation," 

 but finally concluded that it was a term of such wide .vignificance 

 that it could not be well used as the name of any one kind of 

 segregation, while at the same time it was not broad enough to 

 serve as a general term for all kinds. I therefore greatly prefer 

 the term "segregation of the fit." I would, however, so define 

 it as to cover all forms of segregation. 



Though our use of this fundamental word is undoubtedly due 

 L) our having the same general truth to express, several diver- 

 ;4ences appear in the development of our respective theories, 

 tending, we may hope, to a fuller elucidation of the subject. 



76 Concession, Osaka, Japan. John T. Gulick. 



Alpine Haze. 



The peculiar haze mentioned by Prof. Tyndall is no doubt 

 identical with what is commonly met with in some parts of 

 the Mediterranean. During the hottest and driest weather 

 •^if the summer, and when no wind is blowing, perfectly 

 liorizontal strata of haze can be seen occupying the Gulf of 

 \ aples. The peaks of the Sorrentine Mountains, with Solara of 

 ' .'apri, Ischia, Vesuvius, Camaldoli, <S:c., stand out above this 

 aze. The height of the strata rarely reaches 2000 feet, and is 

 I acre often about 1500 feet. The same facts that led Prof 

 lyndall to con^der it other than water vapour, and of micro- 

 "Jganic nature, had produced in my mind similar conclusions. 

 This haze, when looked at near the sea, has often a beautiful 

 link tint, due, no doubt, to a complementary eflect from the 

 L-a-water colour, as the colour is more marked on the limestone 

 r )cks, where the white sea-bottom makes the water look much 

 leener When, however, the observer is cut off from a view 

 f the green sea for some time, the haze has then a light buff 

 olour. The opacity of this haze is so great as sometimes to 

 r semble a slight London fog. 



Anyone who would count the number and study the characters 

 ■ f the organisms and other solid contents of the air here at 

 different times would soon settle the question what this pheno- 

 menon is due to, and whether there is any truth in the old 

 l^liglti- II. T. Johnston-Lavis, 



Naples, November 4. 



The Astronomical Observatory of Pekin. 



In your number of November 8 (p. 46), you gave an account i 

 of a lecture by Mr. S. M. Russell, of Pekin, on the instru- 

 ments in the old Observatory there. May I mention that the | 



late Alex. Wylie, about nine or ten years ago, published a fiill 

 account of them (with illustrations) in the " Travaux de la 3ine 

 Session du Congres International des Orientalistes," vol. 11. 

 Having had my attention drawn to them by some photographs 

 kindly sent me by Mr. Russell, I pointed out the scientific In- 

 terest of Ko Show-King's instruments (which anticipated the 

 ideas of Tycho Brahe by three hundred year.s), in a paper pub- 

 lished in the Proceedings of the Royal Irish Academy, vol. iii., 

 1881, and in Copernicus, vol. i. J. L. E. Dreyer. 



Armagh Observatory, November 12, 



AN HISTORICAL AND DESCRIPTIVE LIST 

 OF SOME DOUBLE STARS SUSPECTED TO 

 VARY IN LIGHT 



THE light-changes of double stars are, for the most 

 part, of an intermittent character. Unmistakable at 

 one epoch, they may completely evade detection at 

 another. Hence observations of them which, by the 

 nature of the case, cannot be repeated are apt to incur 

 discredit for lack of confirmation. They should, on the 

 contrary, if properly authenticated, be carefully borne in 

 mind, as testifying to an incident in the history of the 

 stars they refer to which, however apparently isolated, 

 must be extremely liable to recur. We have therefore 

 thought that it would be useful to put together, as con- 

 cisely as possible, a few facts bearing on the supposed 

 variability of some stars which we may reasonably con- 

 sider to be physically double, referring those of our 

 readers who desire fuller information on the subject to 

 the original authorities we shall cite for their convenience, 

 y Virginis = 2 1670.— The first observation is by 

 Bradley in 17 18, The components, normally of the third 

 magnitude, were regarded as equal by all observers until 

 W. Struve, May 3, 1818, noticed the preceding star as 

 slightly the fainter. It continued so for several years ; 

 the difference was obliterated from 1825-31, and reversed, 

 doubtfully 1832-33, certainly in 1834 (" Mensurae Micro- 

 metricjE," pp. Ixxii. 4.). O. Struve's observations, 1840-74, 

 showed decided variability in a double period, oscilla- 

 tions of half a magnitude in a ^^w days being superposed 

 upon a fluctuation extending over many years. An in- 

 vestigation of the law of change, begun in 1 851, led to no 

 result, owing to the low altitude of these stars at Pulkowa 

 (" Obs. de Poulkova,''ix. 122). Dawes found them equal, 

 1840-47 ; but each alternately about a quarter of a mag- 

 nitude brighter than the other, 1847-54 (Memoirs R. 

 Astr. Soc, xxxv. 217-19). Similar swayings of lustre 

 were constantly apparent to Dembowski {Astr. Nach., 

 Nos. nil, 1185, 1979). Each star is given as of 3'5 

 magnitude (combined 28) in the " Harvard Photometry" 

 (see also '' Harvard Annals," xiv. 454). Gould assigns to 

 them the combined magnitude of 31, Pritchard of 2'67 ; 

 Gore thought them nearer to the second than to the 

 third magnitude, April 5, 1883 ("Cat. of Suspected 

 Variables," p. 362). (The combined magnitude of two 

 third magnitude stars is 2"25.) Owing to their un- 

 certainty of shining, the angle has often been reversed 

 in measuring these stars. They are of a pale yellow 

 colour, and show a spectrum of the Sirian type. They 

 revolve in a highly eccentric orbit in a period of 180 

 years, and emit fully sixteen times as much light 

 proportionately to their mass, as the sun. 



44 (/) Bootis = 2 1909 — On June 16, 1819, Struve noted 

 a difference of two magnitudes between the components ; 

 of one invariably 1822-33, but of only half a magnitude 

 1833^38. Argelander found them exactly equal, June 6, 1830 

 (" Mens. Microm.," p. Ixxii.). To Dawes, in April 1841, the 

 attendant star seemed a shade brighter than its primary, 

 which was rated as of fifth magnitude (Mems. R. A. Soc, 

 xxxv. 232). Duner's observations at Lund, i858 75, con- 

 firm their relative variability, causing the disparity be- 

 tween them to range from 0*4 to i 3 magnitude ; and 

 he points out that they appeared to Herschel consider- 



