42 



NA rURE 



[May 9, 1901 



genus nestling amid a rosette of azure lichen. Other ex- 

 amples show white or yellow spiders in flowers of similar 

 colour, the resemblance, being most complete in the case of a 

 Vatia, whose yellow body is spotted with red to accord with a 

 yellow and red flower. After tracing the gradual evolution of 

 this type of " mimicry " among spiders from the dull-coloured 

 to the bright-hued species, the author refers to certain well- 

 known difticulties as to the origin of resemblances of this 

 nature. 



A LARGE Mycena-an pilhos in the First \"ase Room, British 

 Museum, was inadvertently stated on p. 13, col. i, line 6 from 

 bottom, to have come from lalysos in Rhodes. In reality it 

 was brought froin Knossos itself by Mr. Minos Kalochairinos, 

 who essayed several excavations at Kephala in years gone by. 



We learn, from the Journal of Bolatty, that a new society, 

 to be called the International Botanical Association, is to be 

 inaugurated at a meeting to be held in the botanical laboratory 

 of the University of Geneva on August 7. The chief object of 

 the Association will be "the foundation of a bibliographic 

 jieriodical, criticising in a perfectly impartial manner all botanical 

 publications. . . . The criticisms will, at the desire of the 

 contributors, be published in English, French or German." The 

 editor, who will be responsible to the Association for this ab- 

 solute impartiality and the cyclopcedic knowledge which it in- 

 volves, will be Dr. J. P. Lotsy, of Wageningen, Holland ; and 

 the subscription to the Association, including the periodical, is 

 not to e.\ceed 2\s. per annum. 



The first volume of a " Handbuch der systematischen 

 Botanik," by Prof. R. R. v. Wettstein, has been published by 

 llerr Franz Deuticke, Leipzig and Vienna. The chief object of 

 the work is to present a view of the various forms of plants, 

 with special reference to their phylogenetic development. The 

 volume just received contains an account of the principles of 

 systematic botany and of different plant systems, and a de- 

 scription of the characteristics of six great divisions of the plant 

 kingdom, distinguished as follows : — myxophyta, schizophyta, 

 zygophyta," euthallophyta, phaeophyta and rhodophyta. The 

 cormophytes are reserved for treatment in the second volume, 

 which will appear in the course of next year, when the two 

 volumes will be noticed together. 



The additions to the Zoological Society's Gardens during 

 the past week include three African Sheep [Ovis aries) from 

 Bida Nigeria, a Bateleur Eagle (Helolarsus ecaudatus) from 

 Zebba Nigeria, presented by Mr. Fanshawe Abadie ; a Lion 

 (Fe/is leo, i ) from Africa, presented by Mr. Rowland Ward ; a 

 Chough {Pyrrhocora.x gracuhii), British, presented by Mr. W. H. 

 St. Quintin ; a Black-pointed Teguexin (Tupinavibis iiigro- 

 piinclatus) from South America, presen ted by Mr. G. P. Ogg ; 

 a Turkish Gecko (Hcinidaclylui t uric ins) from Western Asia, 

 presented by Miss Kensington ; six Ceylonese Terrapins 

 (Nicoria trijtiga), a Changeable Lizard (Calotes versicolor) from 

 India, three Blue-tongued Cyclodus ( Tiliijua scincoides), three 

 Black and Yellow Cyclodus [Tiliijua nigrj-luteus) from Aus- 

 tralia, a Chained Snake {Coluber caleuifer) from California, two 

 Ten-lined Snakes (Contia dtcemlineata) from North America, 



two Snakes [Conlia rolhi) from Syria, four Lacertine 



Snakes {Coelopcltis nionspessulana), four \'ivacious Snakes 

 Tarhophis follax), an .I'^sculapian Snake {Coluber foiigissimiis), 

 a Dahl's Snake {Zaiiienis dahli), two Dark Green Snakes 

 (Zaiiteiiis gemonensis), a Comn on Snake {Tropidonotus nalri.x, 

 var.) two Glass Snakes (Ophiosaurus apus). South European, 



two Ground Snakes ( Typhlops vermicularis) from Asia 



Minor, a Black-necked Stork {Xenorhynckus australis) from 

 Malacca, deposited ; two Smews {Mergus albellus), a Velvet 

 Scoter {.-EdeHiia fusca), four Wigeon {Mareca penelope), Euro- 

 pean, purchased. 



NO. 1645, VOL. 64] 



OUR ASTRONOMICAL COLUMN. 



Comet a (1901). — A further telegram concerning the new 

 comet has been received from Kiel announcing its observation 

 at Arequipn, in Peru, on May 2, at 6h. 4S'6m. p.m. Its posi- 

 tion then was 



R.A. = 3h. 30m. 

 Decl. = - 1° o'. 



A later telegram gives particulars of another observation at 

 the Cape at the position 



R.A =3h.^54n^,- 29=. \ ^ay 4d. 6h. 2S 8m. 



Decl. = -o 18 27 ) ^ ' ^ 



Daily Motion in R.A. = -t- 14m. 

 ,, Decl. = + 13'. 



It has been observed at Eastbourne by Mr. Chambers, who 

 saw it about 3.0 a.m. on May 2. Reports in the daily Press 

 also state its frequent observation at Melbourne and the Cape, 

 but its motion is there stated to be north-westerly. 



Stellar Photography with a Siderostat. — Some little 

 interest has been evinced during the past few months in con- 

 nection with the practical elimination of the rotation of the field 

 which occurs when a siderostat is used to follow the diurnal 

 motion. In Comples rettdus (vol. cxxxii. pp. 931-932) Prof. 

 Lippmann suggests a mechanical contrivance, to be attached to 

 the slide carrying the photographic plate, which shall be so 

 geared to the driving mechanism of the siderostat itself as to 

 compensate for the rotation of field. 



Prof. Cornu, in the same number, pp. 1013-1017, calls atten- 

 tion to a method he has previously recommended and which he 

 thinks very good as regards mechanical efficiency. The essential 

 factor is the employment of a universal joint, the angle between 

 the component axes depending on the polar distance of the 

 direction of the reflected beam. The plate holder is rotated by 

 means of a subsidiary mechanism through the medium of the 

 joint. He was led to the device by having to design a 

 mechanism to represent a formula in connection with polarised 

 light in isotropic and other media, this formula being of the 

 same type as that showing the rotation of field of a siderostat. 



From Prof. Cornu's suggestions M. Gautier constructed the 

 necessary apparatus for this purpose, which is used with the 

 50-inch refractor shown at the Paris Exhibition of 1900. 



FORMUL.K FOR VARIATION oi" LATITUDE. — The observa- 

 tions of latitude made by Profs. Doolittle and Gratchof 

 (Aslronoiitical Journal, Nos. 490 and 495) lead Prof. S. C. 

 Chandler to consider that they afford evidence of changes in the 

 annual component of latitude variation ; he therefore proposes 

 to include such changes in the numerical theory, and gives 

 formula; and tables of reduction which may be used for such 

 observations {Astronomical Journal, No. 495). 



Position of Nova Persei. — Prof. E. C. Pickering gives, in 

 the Astronoinische Nachrichten{V,A. 155, No. 3706), the follow- 

 ing mean position adopted from numerous measures with the 

 transit circle at Harvard College Observatory : 



R.A = 3h. 24m. 28-ios. I (,9o,.o). 

 Decl. = + 43 33 54 -^ i ^ ^ ' 



PllOTOGRArHS OF THE ZODIACAL LiGHT. — In Popular 

 Astronomy for April Mr. A. E. Douglass, of the Lowell Observ- 

 atory at Flagstaff', Arizona, describes some successful photo- 

 graphs of the western zodiacal cone which he was fortunate 

 enough to obtain on February 13 of this year. 



The lens he employed was made in 1899 by Messrs. Alvan 

 Clark and Sons especially for this purpose ; its aperture is 

 O'g inch, focus i '8 inches, the intensity being thus 1:2. 



Previous to this date many exposures had been made of an 

 hour or more, but the short exposure tried on the 13th was 

 most successful. It appears that when the zodiacal light is at 

 its best, exposures of about eight minutes are ample ; when not 

 so clear, about thirty minutes should suffice. Glycin or hydro- 

 quinone «eie found most trustworthy for development, the former 

 being especially free from any tendency to produce general 

 fogging of the plate. Reproductions from three of the photo- 

 graphs taken at intervals of a few minutes accompany the paper. 

 They all show some trace of condensation about the centre 

 of the illuminated cone. 



