288 



NATURE 



[November 7, 1912 



K.C.I.E., has just been issued by Mr. Francis 

 Edwards, 83 Higli Street, Marylebone, London, W. 

 A SECOND edition of Mr. A. H. Mackenzie's 

 "Theoretical and Practical Mechanics" has been pub- 

 lished by Messrs. Macmillan and Co., Ltd. The first 

 edition was reviewed in our issue of May 16, 1907 

 (vol. Ixxvi., p. 50). While the general character of the 

 book has been preserved, the new edition has been 

 much enlarged, and in its preparation Mr. Mackenzie 

 has had the cooperation of Mr. A. Forster. The price 

 of the volume remains is. 6d. 



OUR ASTRONOMICAL COLUMN. 



A New Comet, 1912c. — A telegram from the Kiel 

 CentralstcUe announces the discovery of a new comet 

 by M. Borrelly at Marseilles on November 2. The 

 position at yh. 39'9m. (Marseilles M.T.) was : — 



R.A. = i7h. 47m., decl.=3S° 57' N., 

 which lies about 2° N.W. of 6 Herculis. The motion 

 is said to be south-east, the magnitude 10, and the 

 comet transits at about 3 p.m. 



A second telegram from the Centralstelle states that 

 the comet was observed by M. Abetti, at the Arcetri 

 Observatory, on November 3, when its position at 

 7h. 7'6m. (Arcetri M.T.) was : — 



R.A. = i7h. ssm. i2'8s., decl.=37° 21' 5", 

 and the magnitude was estimated at g's. The posi- 

 tion, at present, is favourable for observations during 

 the evenings, when the comet is fairly high up in the 

 north-west sky. 



Gale's Comet 1912a. — Photographic observations 

 made at the Hamburg Observatory, Bergedorf, on 

 October 9 showed the coma of Gale's comet to be 

 elongated in the direction of the chief tail, position 

 angle 79°, and to be about I'l' in diameter; a plate 

 taken with a 5-inch objective of 25-inch focal length 

 showed a tail 5^4° long, which was 2' broad until it 

 reached about 1° from the head, and then broadened 

 out to 11' at a distance of 5°. A shorter tail emerged 

 in position angle 122°, and another was suspected at 

 position angle 50°; the magnitude of the whole comet 

 was about 5^5. 



Spectrographic observations on October 10 and 15 

 showed a bright image of the head at 387 fiJ. +, and 

 the bands at 474 and 563 n/i, the blue band being 

 essentially brighter than the yellow; the band at c,i6 i^fi 

 was much fainter. The continuous spectrum was much 

 fainter than the bands named, but could be seen ex- 

 tending right along the spectrum from 387 to 563 /^m, 

 and was brightest between 397 and 410 /i/'. Prof. 

 Schwassmann states that on the whole the spectrum 

 obtained is very similar to that given by Kiess's comet 

 at the beginning of July, 191 1. {.istronomische Nach- 

 richten, No. 4608.) 



Schaumasse's Comet 1912b. — In No. 4609 of the 

 Aslrononiiache Nachrichten, M. Fayet shows that if 

 the comet recently discovered by M. Schaumasse is not 

 identical with Tattle's comet, the two objects are 

 moving in very similar orbits. If the identity is 

 accepted, there is an error of about 5° in the mean 

 anomalv, and nearly 4" in the mean motion, accord- 

 ing to M. Raht's elements for Tuttle's comet as given 

 in these columns last week. A tentative calculation 

 bv M. Favet does not indicate the near approach of the 

 comet to any great planet during the recent revolution, 

 and he suggests the possibility that the comet may 

 have split up, the object discovered by M. Schaumasse 

 being only one, part. It would be of interest to search 

 ior the main bodv near the calculated positions given 

 in M. MiliSeviC's recently published ephemeris ; on 

 October 20 the position of comet 1912b was 



NO. 2245, VOL. 90] 



a=ioh. 3m., 5=— 0° 43', whereas the ephemeris posi- 

 tion for I'uttle's comet was o = 9h. 37m., 8=4-73° 27'. 

 In a later note (Astronomisclie Nachrichten, 

 No. 4610), M. Fayet states that he finds that near the 

 end of 1900 Tuttle's comet was near Jupiter, the 

 minimum distance being 08, and a rough calculation 

 gives October 9, 1912, as the resulting date of peri- 

 helion passage, three months earlier than the date 

 indicated by the 1899 orbit ; the new value for the 

 mean motion (/j) is 263'94". M. Fayet concludes that 

 the identity of 1912b with Tuttle's comet is very prob- 

 able, but his hurried calculations of the Jovian per- 

 turbation are necessarily only approximate. M. 

 Schaumasse's new ephemeris gives the following posi- 

 tions and distances : — 



Ephemeris I2h. {M.T. Paris). 



Nov. 



15 

 19 



Sundials. — Several interesting articles on sundials 

 are published in the October number of L'Astronomie. 

 M. Roguet describes an elaborate dial recently erected 

 on the south fagade of Juvisy Observatory, and also 

 discusses the history of this instrument, which he 

 believes was invented about 550 B.C. ; this article is 

 illustrated by several interesting photographs and 

 diagrams, the former depicting a large number of 

 ancient, or especially interesting, dials. M. d'Aurelle 

 Montmorin describes tlie "Auto," a new portable sun- 

 dial, and M. Joyeux gives an interesting and detailed 

 description of the sundial erected on the communal 

 school at Sevres. 



Variability of Solar RADi.-iTiON. — Mr. C. G. Abbot, 

 director of the Smithsonian Astrophysical Observatory 

 at Washington, has just returned from a five months' 

 astronomical expedition to Bassour, Algeria. The 

 object of the expedition was to confirm or disprove 

 the supposed variability of the sun. The Astrophysical 

 Observatory has been for seven years making ob- 

 servations on Mt. Wilson, in California, on the daily 

 quantity of heat received from the sun. The observa- 

 tions are arranged in such a manner as to indicate 

 not only the quantity of solar heat reaching the earth, 

 but also the quantity of heat which would reach a 

 body like the moon, which has no appreciable atmo- 

 sphere. 



The observations have indicated that the sun is 

 probably a variable star having a range of variation 

 amounting to from 5 to 10 per cent, within an irre- 

 gular interval of from five to ten days. Last year 

 Mr. Abbot observed in Algeria, while his colleague, 

 Mr. Aldrich, observed on Mt. Wilson, in California. 

 The object of thus duplicating the measurements was 

 to avoid being misled by any local atmospheric con- 

 ditions which might have affected Mt. W'ilson observa- 

 tions. As nearly one-third of the circumference of the 

 earth lies between Mt. Wilson and Algeria, it could 

 not be expected that a similar local disturbance could 

 affect both stations on the same day in the same 

 manner. The observations of 191 1 supported the 

 belief that the sun is variable, but owing to cloudi- 

 ness their number was not sufficient fully to establish 

 this point. Hence it was thought best to return to- 

 Algeria this year. 



The observations made by the Smithsonian party in 

 Algeria this vear were apparently very satisfactory. 

 They occupied sixtv-four days, and on more than fifty 

 of these davs Mr. Fowie made similar observations on 

 Mt. Wilson, in California. The results of the work of 

 lOif and iqi2 are expected to establish the supposed 

 variability of the sun, or to show conclusively that this 

 hvpothesis can no longer be held. 



