i5« 



NA TURE 



[December 19, 1907 



attraction of gravity, and tliis constant direction enables 

 the axis to be leapt inclined at the same angle to the 

 plane of the diagram throughout a revolution. The result 

 is that the terrestrial globe only rotates on its axis once 

 during a complete revolution. This is misleading, and it 

 will be necessary for the teacher to explain that though 

 the device illustrates the different aspects of the earth pre- 

 sented to the sun during the year on account of the con- 

 stant inclination of the axis, it does not represent 

 accurately the relation between the day and the year. 

 With this reservation, the model may be found of service 

 in teaching astronomical geography. 



Messrs. Taylor and Francis have now published the 

 first part of the fourth volume on Rhynchota, by Mr. 

 W. L. Distant, of " The Fauna of British India, including 

 Ceylon and Burma." These volumes are published under 

 the authority of the Secretary of State for India in Council, 

 and edited by Lieut.-Colonel C. T. Bingham. The third 

 volume on Rhynchota was reviewed in Nature of July 5, 

 1906 (vol. Ixxiv., p. 221). The present fasciculus gives an 

 account of the homopterus families Membracidae and 

 Cercopidae, and four subfamilies of the Jassidae. The 

 second part — in the appearance of which there is likely to 

 be some delay owing to the necessity of examining material 

 at present contained only in certain Continental museums 

 — will contain the remaining subfamilies of the Jassidae 

 and an appendix to the whole work. 



Messrs. J. and A. Churchill have published a tenth 

 edition of Valentin's widely known " Practical Chemistry." 

 Prof. W. R. Hodgkinson has added to the present issue 

 easy experimental work in the early chapters, on the com- 

 position of air and water, some carbon compounds, sulphur 

 and sulphuric acid, exercises on quantitative analysis, 

 volumetric analyses, and methods of ascertaining molecular 

 weight. The microscopic structure of some common alloys 

 has been illustrated by photographs, and the whole work 

 revised and brought up to date. The volume now runs 

 to 476 pages, and its price is los. net. 



OVR ASTRONOMICAL COLUMN. 



The Maximum of Mira, 1906. — Mr. Naozo Ichinohe, of 

 the Yerkes Observatory, observed Mira, for magnitude, 

 from October 10, 1906, to March 8, 1907, and publishes 

 his results, with a curve, in No. 4219 of the Astronomische 

 Nachrichten (p. 311, December 5). These show that the 

 maximum brightness occurred on December 12, 1906, 

 which was about seven days before the predicted date. 

 This early date is confirmed by the results of other 

 observers, which give December 13, 12, and 7 respectively. 



A Further Observation of Comet 1907a. — A- telegram 

 to the Kiel Centralstclle from Prof. Wolf states that 

 comet 1907a was re-observed at the Konigstiihl Observa- 

 tory on December 4. At iih. 3-3m. on that date its 

 position was a = 3h. 23m. 40s., 8=4-50° 35', a little to 

 the north-east of a Persei, and its magnitude was 12-5. 

 The motion of the object was found to be in accordance 

 with the ephemeris lAstronomische Nachrichten, No. 4219, 

 p. 315, December 5). 



Spectroscopic Determination of the Rot.^tion of the 

 Sun. — In a paper published in No. 4, vol. x.xvi., of the 

 Astrophysical Journal (p. 203, November), Prof. Adams 

 describes at some length the instruments and methods 

 employed by him at the Solar Observatory, Mount Wilson, 

 in a spectroscopic determination of solar rotation period, 

 and, after discussing them, he compares his results with 

 those obtained previously by Dun^r and Halm. 



In the lower latitudes of the solar disc the recent results 

 agree very well with the values obtained by Dun(5r and 

 Halm, but in higher latitudes they lie between those of 

 the previous observers. The rate of change of the velocity 

 with the latitude attains a maximum in latitude '30°, be- 

 NO. 1990, VOL. "/y] 



coming less in higher latitudes, and almost disappearing 

 beyond 70°. Twenty lines, lying between A 4190 and 

 X 4300, and attributed to different elements, were employed 

 in the research, and it was found that different lines gave 

 different rotational velocities. The titanium line at 

 K 429038 gave a systematically low value, although it is 

 an enhanced line, and might therefore be expected to 

 have its origin in the higher levels of the solar atmosphere. 

 Two lines of manganese, A. 4257-82 and \ 426608, gave a 

 consistently high value. Two carbon lines and a line due 

 to lanthanum give low values, thus agreeing with the 

 conclusion that these two elements reside in the lower 

 layers of the sun's atmosphere. There are no indications 

 of a variable velocity for any one latitude during the 

 fourteen months of observation (May, igo6, to June, 1907), 

 and the results appear to show that the photographic 

 method displays a considerable gain of accuracy over the 

 visual method so far as accidental errors of measurement 

 are concerned. 



Newly discovered Spectroscopic Binaries. — Bulletin 

 No. 123 of the Lick Observatory announces the recent dis- 

 covery of the variable radial velocities of ten stars. Two 

 of these, x Carinae and > Gruis, were found to be binaries 

 on examining plates taken at Santiago ; the other eight 

 were discovered at Mount Hamilton. They are 0, /, and 

 d Tauri, 7 Cameleopardalis, A Bobtis, j3 Coronae, { Cygni, 

 and f Cephei. 



In the same Bulletin Mr. A. B. Turner publishes a set 

 of elements, and a velocity curve, for the spectroscopic 

 binary a Draconis, showing the period to be 5-27968 days 

 and the length of the semi-major axis of the orbit to be 

 2,632,300 km. The velocity of the system is —13-68 km., 

 and the orbit appears to be nearly circular, its eccentricity 

 being only 0-0107. 



The .\strographic Catalogue. — We have received from 

 the Catania Observatory the first part of their contribu- 

 tion to the International .'\strographic Catalogue. Catania 

 undertook the region dec. -1-46° to dec. -1-55°, and the 

 present volume contains the results for the region 

 dec. -H5o° to +52°, R.A. oh. to 3h^ In an introduction 

 Prof. Ricc6, the director of the observatory, describes the 

 instruments employed — photographs of the astrographic 

 equatorial and the micrometer appear as a frontispiece — 

 and discusses the methods followed in the reduction of the 

 plates. The positions (1900) of some 7000 stars are in- 

 cluded in the present work. 



Stars having Peculiar Spectra. — From the examina- 

 tion of Henry Draper memorial photographs, Mrs. 

 Fleming has discovered a number of variable stars and 

 other objects having peculiar spectra, particulars of which 

 are given in Circular No. 132 of the Harvard 

 College Observatory. The Harvard plates show that 

 D.M. -l-66°-7So, given by Dun^r and by Kriiger as a fourth- 

 type star, gives a spectrum at times which contains no 

 bright lines, whilst at other times the spectrum contains 

 H;8 bright ; the intensity of the spectrum also varies in 

 certain regions. 



Weakened Lines in Sun-spot Spectra. — In No. 3, vol. 

 xxvi., of the Astrophysical Journal, Mr. Nagaraja, of the 

 Kodaikdnal Observatory, gives the wave-lengths of, and 

 discusses, 167 lines which he has found to become 

 weakened in passing from the spectrum of the photosphere 

 to that of sun-spots. The photographs from which Mr. 

 Nagaraja obtained his data were taken with a Rowland 

 grating camera fitted up by Mr. Evershed, and include 

 the region F-D. Considering the forty or so lines due to 

 iron, titanium, and chromium given in this region as 

 enhanced lines by Sir Norman Lockyer, and four more 

 recently announced by Prof. Fowler, Mr. Nagaraja finds 

 that the majority of them are weakened in spots. 



Two enhanced lines of iron at X 5169-07 and X 5169-22, 

 one enhanced titanium line (\ 5188-87), and two enhanced 

 lines of chromium (XA 5502-9 and 5621-7) appear to be 

 exceptions, however. With one exception (X 5284-281, Ti), 

 all the titanium and chromium lines weakened in spots are 

 of the enhanced type. A comparison of the chromospheric 

 and spot-weakened lines shows that only a fraction of the 

 former are weakened in spots, and that a large number of 

 the weakened lines belong to the higher levels of the 

 chromosphere. 



