58o 



NA TURE 



[MaV 27, 1906 



in use would have few equals and probably no superiors. 

 The episcopic and diascopic projection apparatus is of a 

 very complete order, and admits of being used for photo- 

 microgfraphic work as well. The dark ground illumina- 

 tors, and also some recently introduced appliances for 

 metallurgical work, are of special interest. An entirely 

 new design of apparatus, adapted for both visual and 

 photographic purposes in metallurgy, is also exhibited, and 

 in this a definite departure from existing methods is to 

 lie seen. The microtomes are also of new design, and are 

 of very substantial construction. A visit to the premises 

 ■of Mr. Leitz at the present moment cannot fail to be of 

 Interest to microscopists, or to those to whom the micro- 

 scope may be of either practical or scientific value. 



/IIr. John Murray has just issued the fourth edition of 

 Mr. W. C. D. VVhetham's book on "The Recent Develop- 

 ment of Physical Science." The book was published first 

 m 1904, and was noticed in Nature of January 26, 1905 

 (vol. Ixxi., p. 291). The present issue is fundamentally 

 tlie same as the third edition published four years ago, 

 though a few additions have been made. 



No. 16S of Ostwald's Klassiker der exakten Wisseii- 

 schaften, published by Mr. W. Engelmann, Leipzig, con- 

 tains papers on the stereoscope by Wheatstone, Brewster, 

 Riddell, Helmholtz, Wenham, d'Almeida, and Harmer, 

 edited and annotated by Mr. M. von Rohr. The volume 

 makes an interesting contribution to the history of the 

 stereoscope for German readers. 



The thirteenth revised and enlarged edition of " Prantls 

 Lehrbuch der Botanik," edited by Prof. F. Pax, has been 

 published by Mr. W. Engelmann, Leipzig. The text has 

 been extended, and now occupies nearly five hundred pages. 

 The price — six marks — for a volume of this number of 

 pages, and almost the same number of figures, is remark- 

 ably low. 



Prof. R. Zsigmondv's valuable work upon the applica- 

 tion of the method of ultramicroscopy to the study of 

 solutions of colloids has been translated into English by 

 Mr. T. Alexander, and published by Messrs. J. Wiley 

 and Sons (London : Chapman and Hall, Ltd.) under the 

 title " Colloids and the Ultramicroscope." An appreciative 

 notice of the original German work appeared in Nature 

 of March i, 1906 (vol. Ixxiii., p. 410). The price of the 

 English edition is 12s. 6d. net. 



OUR ASTRONOMICAL COLUMN. 



A General Solution of the Spectroheliogr.iph. — A 

 paper by M. Deslandres, published in No. 15 of the 

 Comptes rendtis, describes a " general purposes " spectro- 

 "heliograph recently set up at Meudon in which are com- 

 tiined four distinct instruments for the photographic 

 registration of the phenomena of the solar atmosphere. 

 All these instruments are fed by the same coelostat and 

 objective. 



The first is an ordinary spectroheliograph giving the 

 forms of the flocculi in 'Ha light, the dispersion and 

 reflection being performed by a reflection grating. If the 

 grating be removed from the path of the collimated ray 

 the latter falls on a train of prisms, which deviates it 

 into a second camera of 3 m. focal length giving K, and 

 K. images, for comparison with the Ha images, of 80 mm. 

 diameter. 



If h is desirable to isolate a special line the camera 

 objective of the second instrument is replaced by a plane 

 •mirror, so that the ray is reflected into the third spectro- 

 lieliograph arranged for the easy isolation of any special 

 ■radiation, whilst if this instrument be removed the ray 

 ■passes into the fourth instrument, of much greater length 



NO. 2065, VOL. 80] 



and having three slits, so that very fine lines, or definite 

 portions of broad lines, may easily be isolated. It is with 

 the latter form that M. Deslandres has recently obtained 

 the fine images, with K3 and Ho radiations, showing the 

 dark filaments. 



The requisite motions are imparted to the objective form- 

 ing the primary image, and to the photographic plate, by 

 synchronised electric motors and speed transformers, and 

 M. Deslandres states that the change from one instrument 

 to another is a simple matter; the complications 'are more 

 apparent than real. 



The Brightness of the Corona. — Lick Observatory 

 Bulletin No. 153 contains a brief review, by Prof. 

 Perrine, of the results obtained from the attempts to 

 measure the total brightnesses of the corona during the 

 total solar eclipses of 1905 and 1908. 



Among other things, it is shown that the ratio of the 

 intrinsic actinic brilliancy of the brightest parts of the 

 corona to that of the surrounding sky is 744/1, whilst 

 the ratio of total coronal, to full moon, light is O'lii. 

 The results also indicate that there are sufficient differences 

 of brightness of the corona at successive eclipses to be 

 detected by the methods employed at Flint Island in 1908. 



A Standard Scale of Photographic Magnitudes. — In 

 Circular No. 150 of the Harvard College Observatory 

 Prof. Pickering points out the urgent importance of fixing 

 upon some standard scale of photographic magnitudes for 

 international adoption, and describes the work already 

 done in this connection at Harvard. The method of polar 

 sequences, in which the region to be investigated is photo- 

 graphed on the same plate and under the same conditions 

 as the polar region, has been found to give satisfactory 

 results, and the absolute magnitudes of a sequence of 

 forty-seven stars in the latter region have been determined. 

 Other sequences are being prepared, and Prof. Pickering 

 states that the Harvard College Observatory is prepared 

 to devote a large part of its resources to the work if a 

 satisfactory scale can be universally adopted. 



The Origins of Satellites. — In a telegram to the 

 Astronomische Nachrichten (No. 4323, May 17), Prof. See 

 announces that he has rigorously demonstrated that 

 satellites were all captured, and states that he is sending 

 a pap^r setting forth his demonstration. 



The Spectrum of Morehouse's Comet. — With a quartz 

 spectrograph attached to the 8o-cm. refractor of the 

 Potsdam Observatory, Prof. Hartmann obtained a spec- 

 trum of comet 1908c on October 27, 1908 ; the exposure 

 was 140 minutes, and the slit width O'l mm. Three faint 

 pairs of lines are shown at wave-lengths 3874-2, 3908-6; 

 4001-1, 4020-0; and 4252-8, 4275-8. The first of these is 

 very broad, and corresponds to the head of the third 

 cyanogen band, whilst the origins of the other pairs are 

 as yet unknown (/Istronomische Nachrichten, No. 4322). 



The Orbit of { Bootis. — An orbit for { Bootis, 

 previously published by Prof. Doberck, was determined 

 by aid of Sir Wm. Horschel's position angles, and no 

 longer represents the observations. Consequently, Prof. 

 Doberck has determined a new orbit, using only the 

 measures made since 1830, and publishes it, together with 

 an ephemeris until 1915-5, in No. 4322 of the Astrono- 

 tnischc Nachriclitcn ; the following are the elements : — 

 fi='7'° 37 > ^ = 346° 52', 7 = 32° 54', £ = 0-5061, P = 179-60 

 years, T= 1907-84, = 5015", retrograde. The hypothetical 

 parallax of this system is 0-158". 



The Birth of Worlds. — In Cosmophysics, " an inter- 

 national journal of astrophysics," described as the organ 

 of the Wainoni Park Astrophysical Society, Christchurch, 

 New Zealand, Prof. A. W. Bickerton sets forth his com- 

 plete theory of stellar creation. Numerous recent observa- 

 tions of stars, nov£e and their spectra are introduced into 

 this summary in order to demonstrate that lucid stars 

 are formed by the collision of two cosmical masses. The 

 new body, however, is not the combined mass, but, accord- 

 ing to Prof. Bickerton 's theory, is a third body formed 

 by the masses detached from the colliding bodies by the 

 force of the impact ; the latter, after their impact, go on 

 their respective journeys as variable stars. 



