April 6, 191 1] 



NATURE 



191 



decay has started in a tree, its progress is rapid. Decay 

 attacks and disintegrates the dormant tissues first, and 

 gradually works outward. Cement in trees fulfils the 

 three-fold purpose of stopping decay, serving as a struc- 

 tural support, and providing a surface over which the bark 

 may heal. Tree surgery may be likened to dentistry ; all 

 \isting decay must be removed, and means taken to pre- 

 . lit further decay; the cavity must be prepared so that 

 the filling will stay permanently in place, and all foreign 

 substances must be excluded. Chisels and gouges are 

 employed to remove existing decay, which must be 

 followed throughout limbs and trunk so far as it goes. 

 Corrosive sublimate or a similar solution may then be 

 used to destroy any remaining fungi. The walls of the 

 cavity must then be thoroughly waterproofed to protect 

 the wood. Before filling in the cement, the cavity must 

 be well braced, if of considerable size, with steel ribs or 

 truss rods. Skill is required in this matter, so as to 

 allow for the natural swaying of the tree. Water is 

 excluded by cutting a " water-shed " at the edge of the 

 cavity, to which an adhesive waterproofing material is 

 applied. The filling must be under the edge of the bark 

 at every point in order to permit of the bark healing over 

 the filling. 



Messrs. Macmillan and Co., Ltd., have published an 

 Index to vols, xi.-xx. (1901-10 inclusive) of The Economic 

 Journal, the journal of the Royal Economic Society, which 

 is edited by Prof. F. Y. Edgeworth, assisted by Mr. H. B. 

 Lees Smith, M.P. The index has been prepared by Miss 

 Ethel R. Faraday. 



In our issue of December 26, 1907 (vol. Ixxvii., p. 172), 

 attention was directed to Mr. Nasarvanji Jivanji Ready- 

 money's " Science of Nature-History." The author has 

 sent a copy of a reissue of his work — in which he has 

 modified the title and added an introductory page — and 

 also a pamphlet entitled " A Programme of Education," 

 in which he commends the heuristic method of teaching. 



Messrs. Bailli^^re, Tindall and Cox announce that the 

 new edition of Green's " Pathology " will be ready for 

 publication by the end of the month. The work has again 

 Ixen revised by Dr. Bosanquet, much new material added, 

 and rearrangement of subjects made. Its format has also 

 been modified for inclusion in the " University Series of 

 Manuals," which contains such volumes as Stewart's 

 " Physiology " and Dawson Turner's " Medical Elec- 

 tricity." 



OUR ASTRONOMICAL COLUMN. 



Halley's and Faye's Comets. ^ — Dr. Max Wolf records, 

 in No. 4486 of the Astronomische Nachrichten, recent 

 observations of both Halley's (1909c) and Faye's (igioe) 

 comets at the Konigstuhl Observatory. On March 19 the 

 former was still an easy object for the large reflector, its 

 magnitude being about 14-0 ; no nucleus was visible, the 

 comet appearing as a round nebulous disc of about 

 I minute diameter. 



Faye's comet on the same evening was fainter than 

 Halley's, its magnitude as a whole being about 15-0. A 

 sixteenth-magnitude nucleus of about 10" diameter was 

 situated nearer to the southern edge of the circular nebu- 

 ' lous disc ; the comet is still an easy object to photograph 

 with the large reflector ; an observation on March 23 gave 

 the magnitude as 14-5. 



Comet 1910a. — An excellent photograph of comet 1910a, 

 taken on January 28, 1910, with a Voigtliinder " Dynar " 

 objective by Dr. Karl Ik>hlin at the Stockholm Obscrva- 

 i tory, is reproduced as a plate in No. 2, vol. xxxiii., of 

 The Astrophysical Journal. The principal tail extends to 

 a length of 18°, and is bifurcated at its extremity ; in 

 addition, there issues from the slender head a secondary 

 tail 2° long. 



NO. 2162, VOL. 86] 



Prof. Ricc6 gives an account of the Catania observa- 

 tions, photographic and spectroscopic, of this comet m 

 No. 2, vol. xi., of the Memorie di Astrofisica ed Astra- 

 nomia'. He reproduces several drawings and photographs 

 showing the magnificent main tail and the small secondary 

 one. In regard to the latter, he suggests, with great 

 reserve, that its formation may have been an effect of the 

 proximity of the comet to Venus, the distance separatmg 

 them on January 27, 19 10, being about 133 million kilo- 

 metres. The Catania drawings for January 22 and 23 

 show the nucleus to be on the outer, convex edge of the 

 U-shaped tail. 



\ Proposed Method of Determining Spectral Types 

 Quantitatively.— On January 24, 1907, we noted in these 

 columns (Nature, No. 1043, vol. Ixxv., p. 304) the results 

 obtained by Dr. Sebastian Albrecht, then of the_ Lick 

 Observatory, from a study of the varying intensities ot 

 certain lines of compound origins found whilst measuring 

 spectrograms for the determination of radial velocities. 

 Briefly, the author found that, in consequence of the 

 variation in intensity of the components from one spectral 

 type to another, there was a progressive variation of the 

 apparent wave-lengths of the compound lines. Further, it 

 was suggested that, by inverting the problem, it might 

 be possible to determine the finer differences in spectral 

 type by careful measurements of the wave-lengths. 



In the current number of The Astrophysical Journal 

 (vol. xxxiii.. No. 2, March, p. 130) Dr. Albrecht, now at 

 the C6rdoba Observatory, gives the preliminary results of 

 such an investigation. One of the chief difficulties is to 

 state definitely and numerically the intervals between the 

 several spectral types F, G, K, and M of the Draper classi- 

 fication, but this is overriden by arbitrarily taking them 

 as equal, and making Ma and Mb one-tenth of an interval 

 on either side of M. Curves were then constructed with 

 type-intervals as abscissae and variation of wave-lengths 

 as ordinates, so that accurate measurements of the wave- 

 lengths in the spectrum of the star under discussion would 

 show at once the exact position of that star in the classifi- 

 cation ; generally speaking, these curves show that the 

 changes in wave-length are regularly progressive from 

 type F to type M. , , • . 



' To illustrate the application of the method, eight stars 

 were chosen, and the selected variable wave-lengths were 

 measured in each, the results being recorded as weighted 

 departures, in tenths of an interval, from the nearest 

 main type. A considerable variation is shown among the 

 individual results from each of the selected lines, although 

 the probable error of the final result from all the lines is, 

 in each case, not great ; also, the accordance with the 

 Draper classification is fairly good. Dr. Albrecht considers 

 that the scheme is workable, and that when further 

 developed it will afford a ready method of determining 

 quantitativelv the spectral type of the stars observed. He 

 also suggests that in order to avoid special measurement 

 a number of his selected compound lines should be included 

 in all future measurements of spectrograms for the deter- 

 mination of radial velocity ; it would appear, however, 

 that for radial-velocity work it is better to use the purest 

 lines possible. 



Meridian Observations at the Royal Observ.\torv, 

 Belgium.— The second part of vol. xii., of the Annalcs dc 

 L'Obscrvatoire Royal de Belgique contains the detailed 

 results of more than 2000 observations made with the 

 Repsold meridian circle during 1909-10 (June), by MM. 

 Philippot, Delporte, and Jamar. The principal object was 

 to complete the observations of the Hoiles dc rcpdre, but 

 observations of the sun, the moon, and the planets, and 

 of comparison stars for comets and for use in deterniining 

 the movements of certain double stars in Burnham s 

 general catalogue, were also made. Since August, 1909, 

 a Repsold registering micrometer has been employed, and 

 during the same year important modifications were made 

 in the meridian room ; among other alterations, the 

 foundations of the pillars were encased with insulating 

 material to prevent variations introduced by changes of 

 temperature. 



The volume also contains an interestmg account of a 

 comparative study of the errors of two chronographs, one 

 by Gautier, the other by Dent. 



