March 17, 19 10] 



NATURE 



OUR ASTRONOMICAL COLUMN. 



Comet 1910a. — A number of observations, with drawings 

 and photographs, of comet 1910a are published in the 

 March number of the Bulletin de la Sociite astronomique 

 de France. Among others, M. Qu6nisset describes the 

 observations made at the Juvisy Observatory, where photo- 

 graphs of the comet and its spectrum were, taken, and 

 drawings made, between January 21 and February 12. 



A photograph taken on Januan.' 29 shows the secondary 

 tail extending to some distance from the nucleus on the 

 south side of the main tail, with which it formed an angle 

 of about 25° ; on this date the main tail was estimated to 

 be longer than 62 million miles. The fan-shaped extension 

 towards the sun is also shown, and extended to some 

 8' from the nucleus, its northern edge showing the concave 

 form discussed by M. Sola. 



Comte de la Baume Pluvinel reports that the spectro- 

 grams show the nucleus sharply defined in the two prin- 

 cipal radiations of the cyanogen band at A 388, and an 

 Intense image of the comet was produced in the hydro- 

 carbon band near X 472. Between these, the nucleus and 

 tail give a continuous spectrum which presents several 

 condensations, the interpretation of which is still under 

 investigation. 



The observations made at the Lick Observatory are 

 recorded in Bulletin No. 174, and show that considerable 

 changes took place in the spectrum between January* 19 

 and 31. The comet was first seen on January 19 as a 

 fan-shaped cloud several times as bright as Venus at its 

 maximum brilliancy, and spectroscopic observations showed 

 the D lines bright, against a background of sky spectrum ; 

 D, was seen to be much stronger, and to extend further 

 than Dj. The comet, having considerably decreased in 

 brightness, could not be seen the next day, and a great 

 storm prevented further observations until January 26. 

 It was then seen that, in addition to the D lines, the 

 regular cometarv' bands were present. On January 27 the 

 same features were recorded, and an additional brightening 

 was seen just to the right of D. A photograph of the 

 spectrum showed a great similarity to the spectrum of 

 comet 1907^, as photographed by Dr. Campbell, the con- 

 tinuous spectrum being relatively weak as compared with 

 the bands. Observations made on January 31 showed that 

 the D lines and the red condensation had disappeared, and 

 that the spectrum of the tail was continuous, extending 

 to a distance of 1° from the head. 



On February i and 2 spectra were photographed with 

 a prismatic camera, and show that the light of the tail 

 is practically all within the visual region, extending 

 towards the violet but a short distance beyond X 467. 

 Dr. Wright suggests that it may be due to sodium vapour 

 rendered fluorescent by the intense sunlight ; this assump- 

 tion might also account for the faint band seen on the 

 red side of the D lines. 



Dr. Albrecht also made spectroscopic observations with 

 a newly designed grating spectrograph of high dispersion 

 attached to the 36-inch refractor. The resulting photo- 

 graphs, on January 27, show the D lines, D, being not 

 more than one-third the intensity of Dj. The light from 

 a sodium flame was employed as a comparison spectrum, 

 and measures made of the radial velocity of the comet, 

 which was found to be +66-I km., and is believed to be 

 trustworthy within 2 or 3 km. Dr. Albrecht suggests that 

 such observations might be useful in determining the orbit 

 of a comet in rare cases, such as the present, when it is 

 difficult to determine accurate positions. Subsequent 

 obser\'ations showed that between January 27 and 30 the 

 intensity of the D lines must have decreased ten-fold. 



Photographs taken by Messrs. Merrill and Oliver cover 

 the period January 26 to February i. and show the general 

 changes and details well, but no sharp narrow streamers 

 and bright knots or condensations are anywhere indicated. 



In No. 610 of the Astronomical Journal Prof. Barnard 

 reports that cloudy weather prevented photographs being 

 taken at the Yerkes Observatory during the period of the 

 comet's greatest brilliancy, except on January 21 and 24, 

 when fair negatives were obtained. A photograph taken 

 on Februar}' 3 shows the extension beyond the head, 

 towards the sun, to be 12' long. This extension is a pro- 

 longation of the southern edge of the main tail, and is 

 shown on all three photographs taken on that date. 



NO. 2107, VOL. 83] 



A further continuation of Dr. Kobold's ephemeris is 

 given in No. 4393 of the Astronomische Nachrichten, and 

 shows that the comet is still moving very slowly north- 

 wards through Pegasus, the position for March 17 being 

 22h. 27-6m., + 16° 32'. An observation made by Herr 

 Pechiile on March 6 gave corrections of os., +0-5', and 

 showed the magnitude to be about 9-5. 



H.\lley's Comet. — Numerous photographs of Halley's 

 comet have been secured, at the Lick Observatory, with 

 the Crossley reflector and other instruments. The negatives 

 taken on December 11, 12, and 13, 1909, show the coma 

 and faint traces of a cone-shaped tail ; as the angle made 

 by lines from the comet to the earth and sun, respectively, 

 was, on that date, less than 2°, this indicates a fairly 

 well-developed tail. A photograph secured by Mr. Olivier 

 with the Crocker telescope on January 28 shows a tail 

 nearly 1° long. On a negative taken with the Crossley 

 reflector on February' 4 a very fine, sharp, stellar nucleus, 

 less than 5' in diameter, is seen, and the tail appears as 

 a narrow, sharply defined cone ; but similar photographs 

 secured on February 10 and 11 show an entirely different 

 form of tail, the narrow quiescent cone having given way 

 to a tail having several fine streamers radiating from the 

 head ; the two longest streamers are straight, and can be 

 traced to a distance of 20' from the head, while the most 

 southerly one is curved. These changes are also shown 

 on the photographs taken with other instruments, where 

 the tail can be traced to a distance of 40', and doubtless 

 indicate a sudden burst of activity- during the first week in 

 February (Lick Observatory Bulletin, No. 174, p. 183). 



PiDoux's Comet. — It now appears probable that the 

 report of the discovery' of a new comet at Geneva was a 

 mistake. A plate exposed through clouds on February 20 

 showed a V-shaped nebulous form near Halley's comet, 

 and before the identification of this object could be com- 

 pleted, the news arrived that a new comet, in the same 

 position, had been discovered at Cardiff. A plate exposed 

 on February 14, on the same region, showed no trace of 

 the object, but a similar form was seen on the edge of a 

 plate taken on February 16 ; but on a photograph taken 

 ! at Heidelberg on February' 10, which covers the region 

 where, according to calculation, the alleged comet should 

 then have appeared, there is no trace of any such object. 

 As no control plate is available, the existence of the reported 

 comet cannot be confirmed iAstronotnische Nachrichten. 

 No. 4392). 



T//E INTERNA T/ONAL AERO AND A/OTOR 



BOAT EXHIBITION 

 T^HIS exhibition opened at Olympia on March 11, and 

 ^ will continue until March 19. The Society of Motor 

 Manufacturers and Traders, Ltd., supported by the Aero 

 Club of the United Kingdom, are responsible for the 

 organisation, and deserve commendation for the fine collec- 

 tion of machines on show. It will be remembered that 

 the first exhibition of this kind, organised by the same 

 societv, was held last March. Great advances have been 

 made in flying machines during the interval, and the fact 

 that British makers do not intend to be left behind will 

 be evident to anyone who visits Olympia this week. A 

 pleasing feature of the present exhibition is the almost 

 entire absence of " crank " ideas, especially in the full- 

 size machines shown. Such are almost inevitable in any 

 collection of models, but even the model section contains 

 many fine examples of thoughtful design and skilful 

 workmanship. 



Monoplanes comprise by far the larger number of 

 machines in the exhibition. Apart from any inherent 

 advantages of this design, such as space occupied, con- 

 venience in dismounting and packing for transit, and light- 

 ness, there is no doubt that its popularity-, both with 

 makers and buyers, is owing to Bl^riot's flight across the 

 Channel last summer. There are twenty monoplanes, nine 

 biplanes, and one triplane, all of these being full-size 

 machines. In addition, there are two balloons, a dirigible, 

 and a large number of engines and accessories shown 

 separately, as well as motor-boats and launches. In prac- 

 tically every case it is evident that the brains of a skilled 

 engineer have been brought to bear on the design and 

 construction. 



