January 25, 1906] 



NA TURE 



305 



March, 1904, to 255 in March, 1905. Of these 36 are 

 resident, 138 non-resident, and 81 foreign members. The 

 society owes its present position as a mathematical society 

 of international rank largely to the personal exertions of 

 Prof. Guccia, and further evidence of this activity is shown 

 bv the offer of a " Guccia medal " and prize of 3000 francs, 

 to be awarded at the mathematical congress at Rome in 

 1908, for the best essay marking an advance in the theory 

 of algebraic twisted curves. 



Mr. Henry Frowde has published an edition of Words- 

 worth's " Guide to the Lakes," with an introduction, 

 appendices, and notes by Mr. Ernest de Selincourt. 

 Though Wordsworth is, throughout the book, rather the 

 lover than the student of nature, yet the volume contains 

 much that will appeal in a special manner to men of 

 science — for example, the remarks on stone circles — and 

 everything the volume contains will serve to increase the 

 enthusiasm with which scientific students approach natural 

 phenomena. 



The 1906 issue of their " Nature Calendar " has been 

 published by Messrs. George Philip and Son, Ltd. It is 

 a little difficult to understand the plan on which the notes 

 for the months have been arranged, and on what prin- 

 ciple the entries for successive days have been selected. 

 Under the date January 25, for instance, are to be found 

 the following statements : — " Jackdaws begin to come to 

 churches " ; " First appearance of Yellow Wagtail " ; and 

 "Honeysuckle leafing." A young, uninitiated nature 

 student, who observed a jackdaw going to church, or came 

 at ross a yellow wagtail, or found honeysuckle in leaf 

 before January 25, might have his faith in naturalists' 

 calendars seriously shaken. 



A second edition of Prof. Douglas H. Campbell's work 

 on " The Structure and Development of Mosses and 

 Ferns " has been published by Messrs. Macmillan and Co., 

 Ltd. The first edition was published in 1895, and was re- 

 viewed at length in our issue for January 2, 1S96 (vol. liii. 

 p 194). Portions of the work have been re-cast entirely, 

 this being especially the case with the eusporangiate ferns. 

 1 he whole book has been carefully revised and new matter 

 has been introduced, including two special chapters on the 

 geological history of the Archegoniates and the significance 

 of the alternation of generations. Some of the new 

 material is published now for the first time, but much of 

 it is based upon papers written by Prof. Campbell during 

 the last ten years. 



OUR ASTRONOMICAL COLUMN. 



Periodical Comets Due to Return this Year. — Writing 

 to the Observatory (No. 366), .Mr. \V. T. Lynn directs 

 attention to the fact that two known periodical comets air 

 due to return during the present year — Holmes's comet in 

 the spring, Finlay's in the summer. The former has 

 already been noted in these columns. Finlay's comet was 

 red at th' 1 Cape on September 26, 1S86, and per- 

 formed its perihelion passage on November 22 of the same 

 year ; its period is about 6-6 years, and on its return in 

 180; it was first seen by the discoverer himself, and passed 

 perihelion on June 16. On its return in 1899 the comet 

 was unfavourably situated for observation, and so escaped 

 detection. 



A note published in No. 1, vol. xiv., of Popular Astro- 

 nomy mentions six other periodical comets as being due 

 this year, viz. Barnard's (1884 II.), E. Swift's (18.14' IV.), 

 Denning's (1SS1 \".), Swift's (1889 VI.), and the two lost 

 comets, Biela's and Brorsen's. Of these, the first and 

 second will be unfavourably placed for observation ; the 

 third lias not been seen since 1881, but will be more 



NO. 189I, VOL. J^] 



favourably placed this year ; the fourth was very faint 

 in 1889, and any small change in the period may have 

 rendered it wholly invisible. 



The Annular Nebula in Cygnus (N.G.C. 6894). — An 

 interesting photographic study of the very faint annular 

 nebula N.G.C. 6894 has recently been made at the Meudon 

 Observatory by M. G. Tikhoff. Using the 39-inch reflector, 

 the observer obtained four photographs, of which he has 

 measured the two best, taken on September 27 and 

 October 27 with exposures 2h. 20m. and 3h. respectively. 



These photographs showed the nebula to have the form 

 of an elliptical ring with a condensation in the centre, the 

 space between the nucleus and the outer ring being fairly 

 bright. The extremities of the major axis of the ellipse 

 are sharp, but several faint appendices are clustered around 

 the ends of the minor axis. Measurements of the plate 

 obtained on September 27 showed the length of the 

 major axis to be 44"-8, that of the minor axis 37"-3, but if 

 the appendices be included the length of the latter becomes 

 50". 8. The nebula really consists of two rings, a broad 

 outer one and a narrow inner ring, but the duplication is 

 interrupted on the north-west by the star discovered 

 by Lord Rosse in 1855. The outer ring has several con- 

 densations in it, of which the two brightest are nearly 

 opposite to Lord Rosse 's star. 



M. Tikhoff recalls the fact that all observers of this 

 nebula have commented on its similarity to the ring 

 nebula in Lyra, and advances the opinion that it is prob- 

 ably in a later stage of development, lor whereas the Ring 

 Nebula has only one condensation, this Cygnian nebula has 

 many. 



Right Ascensions of the Eros Comparison Stars. — In 

 Nos. 4059-4060 of the Astronomische Nachrichten, Dr. 

 Fritz Cohn, of Kdnigsberg, gives a catalogue containing 

 the definitive positions of the Eros comparison stars con- 

 tained in the two lists iussed by the international com- 

 mittee. The positions are given for 1900-0, and two 

 supplementary tables give the proper motions necessary for 

 reducing the places of the few stars known to be in motion 

 to the equator of 1901-0. 



Observations of Nova Persei (No. 2) and Nova 

 Geminorum. — The results of a series of magnitude observ- 

 ations of Novas Persei and Geminorum are given in 

 No. 4066 of the Astronomische Nachrichten by Dr. K. 

 Graff, of the Hamburg Observatory. The Nova Persei 

 observations extend from March 11, 1902, to August 24, 

 1905, and show one or two apparent oscillations of the 

 brightness. On the latter date the magnitude of this star 

 was recorded as 10-73. 



The record for Nova Geminorum contains the results of 

 six observations made between September 16, 1903, and 

 November 10, 1904, and shows an apparent increase in 

 the brightness between January 20, 1904, and the final 

 observation ; the latter was, however, somewhat uncertain, 

 .mil gave a magnitude of <i2-o. 



On November 28, 1903, Prof. Max Wolf found that the 

 magnitude of Nova Persei on the Pickering scale was 

 11-65, but compared photographically with the stars given 

 bv Father Hagen the magnitude came out as io-6. 



Double Star Orbits. — Prof. Doberck publishes four 

 possible orbits for t Ophiuchi and two for 7 Centauri in 

 No. 4063 of the Astronomische Nachrichten. Of these, he 

 finds, on comparison, that the following agree most closely 

 with observational results : — 



t Ophiuchi 



n = 76 12 

 A=I7 45 

 7 = 66 4 



^=0-5338 



P = 223'82J. 



T=i8i479 



a = I" 307 



y Centauri 



fl = 3 21 

 A = 285 2 

 7 = 8l 47 

 f = 0-2958 



P = 2ii-93^. 

 T= 1851-63 



n =l"-92 4 



The value of the hypothetical parallax for t Ophiuchi 

 is o"o35, and for 7 Centauri o"-o54. In the elements of 

 the latter, the epoch and the longitude of periastron are 

 somewhat uncertain, and for this star the motion is 

 retrograde. 



