January 2, 19 13] 



NATURE 



495 



so bright as to remind him of a great rocket. He 

 describes it as a great white light, with a brilliant 

 head and a long, spreading, and shimmering tail, 

 which cut its way across the whole expanse of the sky. 

 From his position in Manchester the meteor appeared 

 to travel in a direction slightly north of west from 

 a point not far from south. Further details of this 

 phenomenon should prove of interest. 



Ephemeris for Gale's Comet, igi2a. — In No. 4618 

 of the Astroiiomische Nachrichten, Dr. Ebell pub- 

 lishes a daily ephemeris, extending to February 5, 

 1913, for Gale's comet. The comet is now high up in 

 Draco, and is reported to have a nucleus of magnitude 

 10 or II. The following is an extract from Dr. Ebell's 

 ephemeris, which is based on the elements published 

 hi Lick Observatory Bulletin No. 218 : — 



Ephemeris 12 h. {M.T. Berlin) 



a (true) S (true) log r 



h. m. . , 



log A JIag. 



Dec. 27 ... 17 17-6 ... +64 54-5 ... 0'224S ... 01374 ... 86 



31 ... 17 30'o ... +68 14. S ... 0-2389 ... 0-1426 ... 86 



J.in. 4 ... 17 455 ... +71 34-9 ... 0-2529 ... 0-1490 ... 8-S 



8 .. 18 5-9 ... +74 51-S ... 0-2663 ■■• 0-156S ... 89 



12 ... 18 35-1 ... +78 ro ... 0-2792 ... 0-i66i ... 9-0 



16 ... 19 20-1 ... +80 539 ... 0-2917 ... 0-1766 ... 9-1 



The Spectru.m of Nov.\ Geminoru.m, No. 2. — 

 Having secured a number of photographs of the 

 spectrum of Nova Geminorum, No. 2, Messrs. ."Xdams 

 and Kohlschutter give their measures and discussion 

 of the radiations in No. 4, vol. xxxvi., of Tlie Astro- 

 physical Journal. The plates were taken with the 

 Cassegrain spectrograph attached to the large reflector 

 (80-foot focus) at Mount Wilson, and cover the period 

 March 22-May 27. During this period considerable 

 changes took place in the spectrum of the nova, and 

 these are discussed at some length in the paper : the 

 chief nebula line, ^ 5007, was first certainly seen on 

 April 6. 



The authors have measured some hundreds of 

 apparently dark and bright lines in the spectrum, and 

 give observed wave-lengths for four groups of nega- 

 tives, each group covering a definite period ; thus in 

 addition to the wave-lengths for the centres of the 

 bright bands they give wave-lengths for the dark lines 

 which some observers consider to be only parts of the 

 structure phenomena of the bright bands. Generally 

 speaking, the wave-lengths for the centres of the 

 latter agree fairly well with those determined from 

 the Madrid spectra, and published in Nafure on April 

 25 (No. 2217, vol. 89, p. 201), and, possibly, might 

 bear the same interpretation. Ten wave-length values 

 of bright bands are given as reasonably identified with 

 helium lines, although it is somewhat difficult to see, 

 from the list of observed wave-lengths, exactly the 

 type of line, or band, some of them represent. The 

 presence of radioactive substances in the nova's atmo- 

 sphere is not indicated by the Mount Wilson photo- 

 graphs, and the authors consider that the presence of 

 nitrogen, as suggested by Mr. Wright in the case of 

 Nova Lacertae, is probable but scarcely proven. 



The widths and displacements of the bright and dark 

 hydrogen lines are also discussed, and the paper is 

 accompanied by reproductions of a number of excellent 

 spectrograms. 



Observations of S.vturn. — L'Astronomie for 

 December contains the results of some observations of 

 Saturn made by M. J. Camus, with the Mailhat equa- 

 torial of o'lo m. aperture, at the French .Astronomical 

 Society's observatory, on November 7. M. Camus 

 used a power of 230, and he reports that, in front of 

 the planet, the exterior edge of the crape ring showed 

 NO. 2253, VOL. 90] 



marked irregularities appearing in profile as grey 

 patches on the yellowish background of the globe. He 

 was also able to recognise the various tints of the 

 same ring. 



IMPROVEMENTS IN MICROSCOPES. 



CO.ME time ago (N.«-ure, December 14, 191 1) we 

 ■~^ referred to several improvements which Messrs. 

 Beck had introduced into their microscopes, and we 

 noted especially the "handle" model as one in which 

 all risk of damage is avoided to the working parts and 

 adjustments when the instrument is moved. Messrs. 

 Beck now inform us that they have revised the make 

 of their well-known "London microscope" on the 

 handle model. In addition to this, the base and pillar 

 are so designed that although the Continental model 

 has been retained, the position of the centre of the 

 inclining joint has been so placed as to give greater 

 stability when the instrument is in a horizontal posi- 

 tion, whilst not interfering with its vertical rigidity, 

 and the size of the base has been increased to that of 

 their large models to insure perfect steadiness under 

 all conditions. The stage is square and specially 

 large, measuring 4 in. in each direction. The coarse 

 adjustment is by a spiral rack and pinion, so accu- 

 rately fitted that even comparatively high powers can 

 be focussed thereby. The fine adjustment is of the 

 I lever type. The adjustment is obtained by a fine 

 micrometer screw actuating a supplementary pointed 

 rod which impinges upon a hardened steel block work- 

 ing upon the lever. The body tube is 140 mm. long, 

 with a graduated draw tube, in a carefully packed 

 fitting, which extends to a length of 200 mm. 



We have received a catalogue of microscopes from 

 Messrs. W. Watson and Sons, 313 High Holborn, 

 W.C, in which the well-known instruments manu- 

 factured by this firm are fully described. Their micro- 

 scopes are British, both in design and construction, 

 with the result that such points as a tripod foot to 

 ensure rigidity in any position, and sprung fittings 

 with adjusting screws to compensate for wear and 

 tear, are insisted on. On the optical side, perhaps 

 no firm has devoted more attention than Messrs. Wat- 

 son to the subslage condenser. In this connection it 

 is noteworthy that they are now supplying an aplana- 

 tised Abbe illuminator, which has an aplanatic cone 

 of o'65 N.A., that is, 0-15 N.A. in e.xcess of the 

 ordinary type, its total N..A. being i'2o.- At the price 

 of i-fS. 6d. such an appliance is obtainable by all 

 microscopists, and will substantially increase the utility 

 of any optical combination. It is interesting to see 

 that such an improvement in substage illuminators is 

 called for; at least it is reasonable to infer that such 

 a demand has arisen. If it indicates that the average 

 microscopist is at last awaking to the fact that in this 

 direction he has the power greatly to increase the pos- 

 sibilities of his instrument, even if it is of a simple 

 form, then there is much hope in the future for micro- 

 scopy. 



There is another matter of interest referred to in 

 the catalogue. Messrs. Watson are now providing, 

 under the designation *i/i2 in., an objective which is 

 really a 1,14 in. They state that many of the 1/12 in. 

 lenses produced by other makers have really the mag- 

 nification of a 1/14 in., so they determined to suoplv 

 objectives of similar power. Tested with a Reichert 

 1/12 and a Leitz 1/16, the magnification of the new 

 lens is half-way between the two. Its N..^. 

 i'3o and its wonderful definition enable it to 

 resolve difficult test objects. The dots of Siirirella 

 ffemina, for instance, are easily seen with oblique 

 illumination, and the definition is good enough to 



