NATURE 



[September 8, 19 lo 



of the state of our knowledge on animal entozoa and their 

 (■ronomic importance. 



The volume presents evident signs of haste in issue from 

 the press. Some of the papers teem with misprints, some 

 are characterised by an almost complete absence of punctua- 

 tion, while again, in many instances, the language used 

 and the construction of the sentences are so slip-shod as to 

 render them almost meaningless. The volume has a 

 number of excellent illustrations of the staff of the various 

 departments, but the glazed paper on which the book is 

 printed is very trying to the eyes. We may note, too, that 

 on the title-page and cover the laboratories are called 

 " the Veterinary Bacteriological Laboratories," though in 

 the introductory chapter they are termed the " Veterinary 

 Research Laboratories," a better term, we think, for, as 

 we have seen, the work is by no means confined to 

 bacteriology. The laboratory has, we feel sure, under its 

 distinguished head a great future before it, and we venture 

 to offer our heartiest congratulations on its new career. 



H ALLEY'S, COMET 

 A LARGE number of publications dealing with observa- 

 tions of Halley's comet have appeared during the last 

 week or two, and from them we extract a few of the more 

 important results. 



Prof. Barnard, in No. 4431 of the Asironomische Nach- 

 rlchten, deals with the observations he made during the 

 time when the comet was at its least distance from the 

 f.arth. The observations in the early morning were greatly 

 interfered with by clouds and smoky skies, but the con- 

 ditions were better after May 17. Prof. Barnard pays 

 particular attention to the observations made during the 

 early mornings of May 18 and 19, and directs attention to 

 a bright pillar of a luminous character seen near the south- 

 eastern horizon. The main feature was the rather broad 

 beam of light, resembling the beam of a searchlight, which 

 stretched obliquely from the eastern horizon to the Milky 

 Way in .'\quila, a length of 107°. Between 2h. and 3h. 

 a.m. this was very conspicuous, and Prof. Barnard descriiies 

 its dimensions and position with respect to neighbouring 

 stars,_ showing that it was considerably inclined to the 

 ecliptic. This is evidently the phenomenon referred to 

 generally as the tail, but "to the observers at Yerkes there 

 appeared the other mass of luminosity, apparently quite 

 separate from the beam, that extended to the south-eastern 

 horizon. Not having been able to observe the comet 

 regularly prior to .'\ugust iS, Prof. Barnard hesitates to 

 make a definite proposition, but he suggests that this 

 phenomenon was the main tail, whilst the bright beam was 

 only a separate streamer. It involved the ecliptic, and 

 observations on .August 19 showed it to be a real pheno- 

 menon connected with the comet; at 2h. 20m. a.m. it 

 showed a more definite upper edge, bounded, roughly, by 

 the stars $ and 7 Piscium and rj and f .Aquarii, and it 

 joined the brighter beam near 7 Pegasi. Observations 

 made earlier in May showed several streamers, of which the 

 long bright beam seen on May iS may have been one, and 

 they also indicated that on May 18 the breadth of the 

 main tail should have been much greater than the beam 

 actually was. Should Prof. Barnard's surmise prove 

 correct, the evidence for the earth's passage through the 

 tail about May 19 would be greatly strengthened. 



Curious sky effects during May 19 were also recorded, 

 and were unusual enough to suggest a connection with the 

 comet. At noon, and for several hours afterwards, a hori- 

 zontal bar of brilliant prismatic colours, w-ith the red upper- 

 most, was seen in the south at an altitude of about 20°, 

 and around the sun was a prismatic halo of 22° diameter. 



After its passage, the comet was a brilliant object at 

 Williams Bay, and to Prof. Barnard " it far exceeded all 

 expectations as a spectacular display." On Mav 26 the 

 tail could be traced to a distance of 63°, and for 25° of its 

 length was very conspicuous. On May 20 the Head was 

 about 2° in diameter, and appeared like a nebulous star 

 with a yellowish colour, but on May 24 it was recorded 

 as bluish-white. On this date, however, there was appar- 

 ently a double nucleus. To the naked eye and with opera- 

 glasses there appeared a nucleus of sensible diameter and 

 of a beautiful bluish-white colour, whilst in the 5-inch 

 finder this was seen to be but an intense nebulosity 

 NO. 2132, VOL. 84] 



jurrounding a smaller, well-defined nucleus of eighth or 

 ninth magnitude, and of a decidedly yellow colour. ITius 

 naked-eye and telescopic observations on that date would 

 refer to two different nuclei of opposite colours. For 

 several nights about May 27 the tail appeared to diffuse 

 northwards as high as Jupiter, and on a photograph taken 

 on June 6 it is seen that the comet had discarded its tail, 

 which was drifting away from it, and had formed a new 

 one at a slightly different position-angle. 



In the same journal Herr Sykora records an observation 

 of the comet on the solar disc at 20-95h. (M.T. Tashkent) 

 on May 19. A 13-cm. image of the sun was projected, 

 and the comet was seen, like a finger-mark on paper, with 

 a diameter of i cm. ; during the three minutes that observa- 

 tions were not prevented by clouds, the relative motion of 

 the supposed cometary image was about 0'5 cm. 



Dr. Hartmann also contributes a note on the measures 

 of the surface brightness of the comet made at Sonnwend- 

 stein. First he suggests that, instead of such indefinite 

 terms as "bright," "faint," &c., a definite scale of 

 standardised surface-brightnesses should be employed, the 

 standard unit being referred to a definite illumination pro- 

 duced by a standard lamp under defined conditions. This 

 unit is called a phos (ph.), a thousandth part of it a 

 milliphos [mph.), a millionth part a microphos (mkph.); 

 for the multiples the prefixes kilo- and mega- are sug- 

 gested. Then he describes a method of using the photo- 

 meter where the image of the object is seen through a 

 hole pierced in a mirror fixed in the focal plane of the 

 objective. By measured variations of the source of 

 illumination, the surface of the mirror is brought to the 

 same brightness as the focal image of the object. .Again, 

 by using suitable screens, the different radiations from any 

 object may be directly compared, and for Jupiter Dr. 

 Hartmann finds a range from red to green of 27 to 6H 

 mph. (milliphos). 



The results obtained by this method, comparing various 

 parts of the comet on different dates, are very interesting. 

 They are too numerous to give fully here, but one or two 

 examples will serve to illustrate them. May 23, gh. 2m. 

 (M.E.T.), mean brightness of nucleus and the surrounding 

 area of 22" diameter: white, 220 mkph., yellow, 180 

 mkph., green, 410 mkph. ; qh. 27m., nucleus alone : white, 

 620 mkph., red, 360 mkph., orange, 630 mkph., yellow, 

 730 mkph., green, 1350 mkph. On May 26 a number of 

 observations, including the nucleus, the area surrounding 

 it, and the tail, were made, and for the tail, at 3m. 42s. 

 in R.-A. behind the head, a value of 022 mkph. was found. 

 For comparison. Dr. Hartmann found on May 31 that the 

 surface brightness of the Ring Nebula was 1-2 mkph., 

 and for the inner space 0-6 mkph. ; a bright area of the 

 Milky Way, in Cygnus, gave a value of 0-05 mkph. 



M. .Antoniadi suggests that the tail, seen by Prof. 

 Eginitis, turned towards the sun on May 20, was only a 

 m.inor sheath ; his observations, and those of Dr. Hart- 

 mann and others, show the tail as a sickle-shaped object 

 with its convex side turned sunwards. 



That the comet was a fine spectacle at Tokio is shown 

 by a table giving the magnitude, length of tail, &c., as 

 seen by Mr. K. Saotome, of the Tokio Observatory, 

 reproduced in the Astronomische Nachrichten. 



In No. 4433 of the same journal Drs. Cowell and 

 Crommelin discuss the different elements published by 

 various calculators for the 1910 osculation. These agree 

 fairly well except in the value given for the mean motion 

 (fi), in which there are grave differences. M. Iwanow 

 .adopted Pontecoulant's value for 1835, which the Greenwich 

 observers have shown to be 005" in error, and should 

 therefore have arrived at a perihelion date differing from 

 theirs by about one month. That this is not so indicates 

 that some serious error crept into his calculations, and it 

 is suggested that, as the difference is so important from 

 a gravitational point of view, the discordance should not 

 be allowed to remain unproved. Mr. Merfield and Messrs. 

 Crawford and Meyer appear to have deduced their value 

 of fi from the recent observations alone, a procedure which 

 Drs. Cowell and Crommelin deprecate as untrustworthy ; 

 and the value obtained by the Berkeley computers is 

 enormously in error. .According to the Greenwich calcu- 

 lators, the value for igio is ^ = 46-6747'', but this cannot 

 yet be accepted as definitive. 



