February 15, 1906] 



NA TURE 



375 



In the Atti dei Lincei (series 5, vol. xiv., ii., 207) Prof. 

 A. Righi describes a number of experiments which were 

 made with the purpose of ascertaining the influence of 

 the rays of radium on the resistance of certain solid and 

 liquid dielectrics. A marked increase in the conductivity 

 under the influence of the rays was observed in the case 

 of liquid vaseline and olive oil, but with benzene, petro- 

 leum ether, and carbon bisulphide a much smaller effect 

 was found. When solid colophony was subjected to the 

 action of the rays, a change of conductivity could not be 

 detected. 



A work upon steam turbines, by Messrs. T. Stevens and 

 II. M. Hobart, giving the most recent results in practice 

 and having a concise account of the latest types, will be 

 issued by Messrs. Whittaker and Co. in March. 



Messrs. Swan Sonnenschein and Co., Ltd., have now 

 published the " Public Schools Year-book " for 1906, 

 being the seventeenth issue of this important annual. 

 Among other useful chapters which the volume contains, in 

 addition to full particulars of 117 public schools, those 

 dealing with engineering, medicine, agriculture, and horti- 

 culture as professions are of particular value to parents 

 desiring occupations for their boys. 



Mr. Francis Hodgson has published the third volume 

 of the second series of the Proceedings of the London 

 Mathematical Society. The volume runs to 482 pages, 

 and includes papers read before the society during the 

 period December 8, 1904, to November 9, 1905. As the 

 papers read at meetings of the society are briefly described 

 in our " Societies and Academies " columns, there is no 

 necessity for a detailed statement of the contents of the 

 volume, though it may be added that, in addition to the 

 papers, the volume includes records of the proceedings at 

 meetings and an obituary notice of the late Mr. Robert 

 Tucker by Prof. M. J. M. Hill, F.R.S. 



OUR ASTRONOMICAL COLUMN. 



Comet 1905c (Giacobini). — Herr A. Wedemeyer gives 

 a continuation of his daily ephemeris for comet 1905c in 

 No. 4074 of the Astronomische Nachrichten. The follow- 

 ing is an extract therefrom : — 



Ephemeris 12I1. M.T. Berlin. 



1906 a (true) 5 (true) log r log A Bright- 



h. m. s. ne« 



Feb 18 ... o 49 32 ... - 13 26 ... 99192 ... 01123 ... 2 91 



20 ... 1 23 ... -11 55 ... 99424 ... 0-1237 ... 2-48 



22 ... I 13 48 ... - 10 27 ... 9 9640 ... CI355 ... 2'13 



24 ... 1 24 45 ...- 9 2 ... 9-9843 ... 0-1477 ... 1-83 



26 ... 1 35 o ... - 7 41 ... 0-0034 ... 0-1602 ... 1-58 



28 ... 1 44 37 ... - 6 24 ... 00214 •■■ 0-1728 ... 1-38 



Brightness at time of discovery = 10. 



It will be noticed that the comet has rapidly decreased 



in brightness, and, as its magnitude when discovered was 



only about io-o, has become a more difficult object. On 



February 18 it will set about 2\ hours after sunset in the 



south-west. 



Comet 1906a (Brooks). — Several observations of comet 

 1906a are recorded in No. 4073 of the Astronomische 

 Nachrichten, in which also appear a set of elements and 

 an ephemeris calculated by Herr M. Ebell. 



The magnitude of the comet on January 2S-31 was 

 about 100, and Prof. Hartwig, observing with the Bam- 

 berg heliometer on the latter date, recorded that the comet 

 was round, had no tail, and had a central nucleus which 

 appeared to be about one magnitude fainter than a 93 

 magnitude star. 



The latter part of Herr Ebell 's ephemeris is given 

 below : — 



NO. 1894, VOL 73] 



12h. M.T. Berlin. 

 (true) 5 (true) log 



log A Cright- 

 9-9742 099 



1906 



h. m. s. 



Feb. 16 ... 12 4 44... +8435 ... 0-1909 



17 ... 10 35 41 ... +8448 



18 ... 9 13 22 ... +84 15 .. 0-1955 9 9S17 - 94 



19 ... 8 12 51 ... +83 8 



20 ... 7 32 10 ... +81 43 ... 0-2001 . 9 9912 ... 0'88 



Although near to the pole, the comet is not an easy 

 object, owing to its small magnitude, which is now- 

 decreasing. 



Observations of Eros. — The results of a number of 

 observations of Eros, made at the Arcetri Observatory 

 between July 26 and August 25, 1905, appear in No. 4073 

 of the Astronomische Nachrichten. 



Variations in the magnitude of the asteroid were 

 observed as follows: — July 28, mag. = n-4; August 7, 

 mag. = 109; August 23, mag. = 120. 



Comets 1905b and 1905c were also observed at Arcetri, 

 and the results are given in the same journal. 



Catalogue of Stars within Two Degrees of the 

 North Pole. — Publication No. 2 of the Vassar College 

 Observatory is devoted to a catalogue of 408 stars all of 

 which are within 2° of the North Pole. The coordinates 

 and magnitudes have been determined from eight plates 

 taken by Prof. Donner, of the Helsingfors (Finland) 

 Observatory, by Dr. Caroline E. Furness. A previous 

 publication (No. 1) dealt similarly with the stars situated 

 within i° of the pole, and to this the present volume forms 

 a sequel. The positions are given for iSSS-o, and in cases 

 where the star is common to both, references are given to 

 the B.D.M. and Carrington catalogues. The present work 

 is published by the Carnegie Institution, and forms No. 45 

 in the publications of that body. 



The Fire near Mount Wilson Observatorv. — Writing 

 to Popular Astronomy, No. 2, vol. xiv.. Prof. Hale corrects 

 the recent report concerning the forest fire on Mount Lowe, 

 and states that, as the fire did not come within several 

 miles of the Solar Observatory, the observers there were 

 never in any fear that the buildings or instruments might 

 be injured. 



The Increasing Period of Lyr/e. — In an article pub- 

 lished in No. 367 of the Observatory, Dr. Alex. W. Roberts 

 makes an interesting suggestion concerning the diminish- 

 ing rate of increase in the period of /3 Lyra-. 



Having discussed a number of previous observations, he 

 has deduced a formula which gives the period of this 

 variable at any date, the epoch being 19000. The sug- 

 gested cause is that in $ Lyrae we have a binary in which 

 the component stars are slowly receding from each other 

 under tidal forces, and if this is so it provides direct 

 evidence in support of Prof. Darwin's theory regarding the 

 evolution of planetary and stellar systems. 



The United States Naval Observatorv. — Rear-Admiral 

 Chester's report of the operations of the United States 

 Naval Observatory for the fiscal year ending June 30, 

 1905, shows that the staff is again to be congratulated 

 on the amount of work performed. Nearly 950 observ- 

 ations, including 218 of Saturn's satellites, were made with 

 the equatorial, and 9179 observations were made with the 

 meridian instruments ; the latter included nearly 4000 

 observations of Gill's " zodiacal stars " and an equal 

 number of " standard stars." 



The A.G. Zone Catalogue of the stars between —13° 50' 

 and — 18 10' is nearing completion ; all the stars have 

 been observed, and most of the observations have been 

 reduced to 1900-0. 



With the photoheliograph, photographs of the sun were 

 obtained on 166 days, and showed spots and faculas on the 

 solar disc on 162 days. Whilst engaged upon this work, 

 Mr. G. H. Peters made some valuable observations regard- 

 ing the focal variation due to temperature. A new triple 

 lens of yl inches aperture and 65 feet focal length, giving 

 a solar image of about 7 inches diameter, has been pro- 

 cured, and was to be used for solar photography after 

 its employment on the 1905 eclipse expedition to Spain. 



The branch observatorv at Tutuila, Samoa, was, on the 

 date of the report, rapidly approaching completion. 



