March 4. 1909I 



NA TURE 



19 



MtssRS. H. W. Cox AND Co. have issued a new calu- 

 loguo of electromedical apparatus, which contains, in 

 .iddition to the descriptions of the apparatus, short sketches 

 uf the theories of their action, and instructions how best 

 to set them up. It should prove of exceptional value to 

 medical practitioners who have not had the advantage of 

 a practical training in the manipulation of physical 

 apparatus. 



We have received from Washington a copy of the report 

 of the Librarian of Congress and of the report of the 

 superintendent of the library buildings and grounds for 

 the fiscal year ending June 30, 1908. Like all American 

 reports, it is of a detailed and exhaustive character, and 

 provides information as to accessions, expenditure, new 

 arrangements, and other matters of particular importance 

 to librarians. It is of interest to note that, in addition to 

 the Library of Congress, with its million and a half books 

 — to say nothing of manuscripts, prints, maps, and charts 

 — there are above a score of libraries maintained by the 

 Federal Government at Washington. Among these may 

 be mentioned those of the Department of Agriculture with 

 00,000 volumes, the Bureau of Education with 82,000, the 

 Geological Survey with So, 000, the Patent Office with 

 So,500, and ,the National Museum with 20,000. Some of 

 the special collections, like that of the U.S. Geological 

 Survey, are unique in character, so it is easy to see that 

 the American student is very fortunate in his facilities for 

 reference to standard authorities and original sources. 



OVR ASTRONOMICAL COLUMN. 

 The Spectra of ^'AUIOl.'s Nebul.=e. The spectra of 

 several nebula, as photographed at Heidelberg with the 

 Waltz reflector, are briefly described by Prof. Wolf in 

 No. 4305 of the Astronomische Nachrichicn (p. 151, 

 February 16). 



Prof. \\"olf states that the planetary nebula N.G.C. 

 62io = B.D. + 24°.3048 is so bright that he is able to photo- 

 graph the ten lines of its spectrum with only a brief ex- 

 posure. These include six of the chief lines, at \K 501 (i.), 

 434 (iii.), 410 (iv.), 397 (v.), 387 (vi.), and 373 (vii.), lines 

 at \K 412, 447, and 496, and H/3 ; the second nebula line, 

 at \ 469, is not recorded, and H7 is clearly double. 



The Ring nebula in Lyra shows the seven chief lines, 

 H/3, and the line at X 496, but no spectrum of the central 

 star is registered. Exposures without the spectrograph 

 give an image of the ring in twenty seconds, but give no 

 trace of the star, thus showing that the latter is less 

 active, photometrically, than the ring itself. Using 

 Wrattcn and Wainwright's " panchromatic " plates, Prof. 

 W'dlf also got the C line of hydrogen registered, and found 

 it to be as bright as the other hydrogen lines. By using 

 ;in open slit, annular images showing the monochromatic 

 forms and sizes of the nebula were obtained ; the ring at 

 A 469 was found to be the smallest, whilst that at A 373 

 is the largest. 



Long exposures on the cluster of nebulae near the galactic 

 pole (i2h. 53m., 4-28°-6) showed continuous spectra with 

 maxima, but the condensations are too weak to measure. 

 The spectrum of N.G.C. 6960, HV 15 Cygni, is purely 

 gaseous, the brightest line being that at A 373, followed by 

 A 434 (H7). and traces of other lines. N.G.C. 6992, 

 HV 14 Cygni, shows the same spectrum with the addition of 

 H/3. The Milky Way nebula, N.G.C. 2023, again shows 

 the lines at AA 373, 434, and 486, but the line A 373 is 

 abnormally bright, and there is a suspicion of an additional 

 line at about A 345. 



The Proposed Progr.\mme of Work for the Reynolds 

 Reflector at Helwan, Eovpt. — From a note in No. 27, 

 vol. ii., of the Cairo Scientific journal (p. 417, December, 

 1008), we learn that the Reynolds reflector at the Helwan 

 Observatory is to be used, primarily, for the photography 

 of nebul;e lying between the equator and 40° south 

 declination. 



NO. 2053, VOL. So] 



Mr. Knox Shaw shows that the instrument, owing to 

 its comparatively short focal length, is unfitted for work 

 on the sun and moon, whilst the absence of a large finder 

 renders the photography of faint satellites impracticable; 

 the ratio of the focal length to the aperture (30 inches) 

 is only 4-5. 



In the proposed zone there are between two and three 

 thousand known nebula-, of which the great majority have 

 as yet onlv been observed visually, and, according to 

 Keeier's estimate of their distribution, there should, in 

 such a zone, be some 40,000 ; it therefore appears that the 

 Reynolds reflector is provided with a very useful pro- 

 gramme for a lengthy period. 



Observations of Comet TempeLj-Swift.— In No. 4306 

 of the Astronomische Nachrichten (p. 159, February 18) 

 Prof. Barnard records his observations of the periodic 

 comet, Tempelj-Swift (i9o8d), during its recent reappear- 

 ance. Observations were made on four days in December, 

 1908, and the comet was found to be a small faint body 

 of less than the sixteenth magnitude. 



A new double star and two new nebute were discovered 

 durin"- the observation of the comet, and Prof. Barnard 

 found that the star B.D.-h43°.53 is one of the finest 

 crimson stars in the heavens ; on December 20, 1908, he 

 recorded it as an exquisite object as seen in the 40-mch 

 refractor. 



The Levels of Sun-spots.— From Mr. Dodwell, of the 

 Observatorv, .Adelaide, we have received a stereogram 

 which confirms Dr. Krebs's observation of the different 

 levels of sun-spots, referred to in this column for August 

 27, iqo8 (No. 2026, vol. Ixxviii., p. 402). 



The two photographs from which the stereogram w'as 

 prepared were taken by Mr. A. W. Dobbie, of Adelaide 

 during the solar eclipse of 1905. and the two groups of 

 spots then visible on the solar disc distinctly appear tobe 

 at difTerent levels. Mr. Dobbie used an i8-inch Newtonian 

 reflector of 13 feet focal length, made by himself, and 

 stopped down to an aperture of 45 '"^^es The exposures 

 given were of about i/ioooth of a second duration, and the 

 interval between the two was about 2J hours. 



A New " Cave-neeula " in Cepheus.— On a plate taken 

 bv him with the Bruce telescope at Heidelberg, on October 

 2i, 1908, Dr. Kopff discovered an interesting nebula in 

 the constellation Cepheus. «-.>i.. 



Later photographs taken by Prof. Wolf, with the Waltz 

 reflector, show this object to be a good example of he 

 singular phenomenon of cave-formation amongst Milky 

 W^-Ty stars. The star B.D.-(-69°.i23i is involved m the 

 nebula, which is situated at the southern extremity of a 

 long, starless space covered with intricate ^""uA I 

 nebulous matter and dark areas, and traversed by a bridge 

 of stars, from east to west, at about 22h. loni., -(-70 o. 

 The position (18550) of the B.D. star is a = 22h. 10m. is., 



~\ reVoduction of the region showing this interesting 

 object accompanies Prof. Wolf's paper describing it in 

 No. 2, vol. Ixix., of the Monthly Notices (R.A.!5-). 



The Recent Magnitude of Nova PERSEi.—Tn No- 4.>o3 

 of the Astronomische Nachrichten Prof. N.jland publishes 

 the results of a series of magnitude observations of Nova 

 Persei (No. 2) made at the Utrecht Observatory between 

 July 1904, and April, 1908. The apparent variations if 

 real are unimportant and irregular, the four yearly va ues 

 being 10-63, 10 S3, 10-58. and 10-59. mean 10-58 ; on Father 

 Hagfn's scale 'his magnitude lies half-way between his 

 stars 42 and 49. 



Double-star Measures.-Nos. 4301 and 4302 of the 

 Astronomische Nachrichten are devoted, to the extent of 

 eighteen three-column pages, to the results of recent micro- 

 meter measures of double stars, made by Prof. Burnham 

 with the 40-inch refractor of the Yerkes Observatory. The 

 measures form part of the observer's general programme 

 of observing neglected doubles, to investigate proper 

 motions, and to provide material which may in future have 

 special value in any discussion of the pairs given in the 

 general catalogue. u ■ j- -j .,» 



A series of notes, dealing respectively with the individua 

 systems, is also given, and will undoubtedly prove useful 

 in any subsequent discussions. 



