520 



NA TURE 



[April 2, 1^08 



been made clear. The explosive material is obtained by 

 treating the zinc alloy of the platinum metal with an 

 acid, and has been regarded as an allotropic modification 

 of the metal. In the Zeitschrift Jiir physikalischc Chemie 

 for Kebruary 25 is an interesting account, by E. Cohen 

 and Th. Strengers, of a long series of experiments on 

 this subject. It was found that the residues from the 

 action of hydrochloric acid upon zinc alloys of rhodium, 

 iridium, ruthenium, and platinum are explosive ; palladium 

 and osmium do not furnish explosive residues. Explosive 

 rhodium is now shown to contain both oxygen and 

 hydrogen, and if air is carefully excluded during the 

 removal of the zinc by the acid, the residue is not explosive. 

 The heat evolved during the explosion was measured, and 

 found to be of the same order of magnitude as the heat 

 of combination of the quantities of hydrogen and oxygen 

 actually occluded by the metal. The most probable ex- 

 planation of the explosive properties of these reduced 

 platinum metals is that the explosion is due to the sudden 

 combination of the occluded hydrogen and oxygen. It 

 was found, however, that in the case of ruthenium an 

 explosive material was obtained even if oxygen vas 

 rigorously excluded during the separation from zinc, and 

 this point still remains to be cleared up. In one of the 

 calorimetric measurements, 4 grains of the rhodium 

 destroyed a platinum calorimeter. A photograph of the 

 remains of the calorimeter after the operation is given, 

 and the authors remark that the effeft of the explosion of 

 a pound of this material (the quantity Bunsen had in the 

 experiment above mentioned) can be easily imagined. 

 Bunsen, fortunately, escaped with superficial burns on the 

 face and severe burns on the hands. 



The narrie of Dr. R. W. Stewart should have been 

 given as the author of the books on heat, light, and sound 

 for matriculation candidates reviewed in Nature of 

 March 26 (p. 4S2). 



Mr. H. J. Glaisher has published the April issue of his 

 catalogue of publishers' remainders; it contains particulars 

 of many scientific and other books which, though in a new 

 condition, are offered at greatly reduced prices. 



Messrs. Oliver and Bovd have published a second 

 edition of " Structural and Field Geology for Students of 

 Pure and Applied Science," by Prof. James Geikie, F.R.S. 

 The first edition of this work was reviewed at length in 

 Nature of July 6, 1905 (vol. Ixxii., p. 223), and the present 

 issue differs but little from its predecessor, though some 

 omissions have been supplied and a number of emendations 

 and corrections made. 



OUR ASTRONOMICAL COLUMN. 

 Astronomical Occurrencbs in April: — 

 April 4. Ih. 24m. Venus in conjunction with Moon. Venus 

 S' 52' N. 

 ,, ih. 2Sm. M.trs in conjunction with Moon. Mars 



4° 15' N. 

 ,, 3h. 27in. Venus in conjunction with Mars. Venus 



i'37'N. 

 9. loh. 55m. Jupiter in conjunction with Moon. 



Jupiter 1° 21' S. 

 14. Iih. 56m. Minimum of Algol ($ Persei). 

 17. 8h. 45m. Minimum of Algol (0 Persei). 

 19-22. Epoch of April Meteors (Radiant 27i°-l-33'). 

 20. Venus. Illuminated portion of disc = o'540. 

 22. 3h. 12m. Uranus in conjunction with Moon. 



Uranus O' 27' N. 

 24. 4h. 45m. to 8h. 27m. Transit of Jupiter's Sat. III. 



(Ganymede). 

 20. 7h. Venus at maximum elonga'ion (45° 37' E.). 



NO. 2005, VOL. yy] 



Comet 1907 II. — We have received an abstract of a paper 

 read by Prof. E. Weiss before the Vienna Academy of 

 Sciences on February b, in which the author directs atten- 

 tion to the striking similarity of the orbit of comet 1907 II. 

 to that of the comet of 1742. It appears probable that 

 they refer to the same body, having a period of 165 years. 

 From the fact that the earth passes very near to the 

 ascending node of the cometary orbit towards the end of 

 March, Prof. Weiss expects that a fairly rich meteor 

 shower, from a radiant at a = 3o7°-6, 5=— Co"-/, should be 

 observed in the southern hemisphere. 



The President of the Astrographic Congress. — At the 

 request of several members of the permanent committee 

 of the Astrographic Congress, Sir David Gill has, we 

 understand, proposed to the permanent committee that M. 

 BaiUaud, the new director of the Paris Observatory, should 

 be elected president of the international congress in 

 succession to the late M. Loevvy. Remembering the 

 important part played by France in the labours expended 

 on the Carte du Ciel, the generous support of the Insti- 

 tute of France in the publication of the committee's re- 

 ports, and the great and successful efforts of Admiral 

 Mouchez, M. Tisserand, and M. Loewy in the furtherance 

 of the work, it is almost as a matter of course that the 

 director of the Paris Observatory should be elected to fill 

 the important position of president of the international 

 committee. 



The Helium, D3, Line in the Solar Spectrum. — In 

 No. 394 (March, p. 133) of the Observatory, Captain Daunt 

 continues the discussion as to the presence of D, as n 

 dark line in the solar spectrum, raised by the photographs 

 taken at Kodaikanal by Mr. Nagaraja last year, and comes 

 to the conclusion that the fine dark line shown on the 

 photographs is not an absorption effect of D^ at all. The 

 main objection raised by Captain Daunt is that the fine 

 dark line on the photographs runs right across the spec- 

 trum, and is sligtly widened over the spot, whereas, 

 according to his own and to Mr. Buss's observations, the 

 helium absorption line is generally very broken and patchy, 

 and has never been seen over the spot itself ; it always 

 appears in the faculic areas surrounding the spot. 



Two Remarkable Spectroscopic Binaries. — In a note 

 published in the Observatory (No. 394, p. 139, March) Mr. 

 Gore shows that two spectroscopic binaries, a Carina; and 

 a Pavonis, recently discovered at the Lick Observatory, 

 must have remarkably small masses. In the case of the 

 former, if the inclination of the orbit be 90°, the mass is 

 but 0-007 of 'hE sun's mass, and if the inclination is 30° 

 this value is only increased to 0-056. The corresponding 

 mass values for a Pavonis are 0-00047 ^""^ 0-0038 re- 

 spectively, and in this case the result is more remarkable 

 still, for o Pavonis is a brighter star, mag. 2-12; its 

 spectrum is of the Orion type. Mr. Gore suggests that 

 both these stars are probably near our system, and an 

 effort should.be made to determine their parallaxes. 



VARi-vrioN IN the Radial Velocity of $ Urs^ Majoris. 

 — In No. 4239 of the Astronomische Nachrichten Dr. H. 

 t.udendorff announces that plates taken at Potsdam show 

 the radial velocity of 3 Ursa; Majoris to be variable. The 

 values given range from —6 km. (March 27, 1904) to 

 — 26 km. (April 28, 1905), and in a footnote it is stated 

 that later observations show the period to be twenty-seven 

 days. 



i)R. Nokdmann's Variable Star Observations. — Follow- 

 ing up the researches mentioned in these columns last week 

 (p. 497), Dr. Charles Nordmann has obtained equally 

 striking results from observations of Lyra; and 8 Cephei. 

 In these cases the epochs of maxima and minima, as 

 observed through the coloured screens, agree with_ the 

 ephemeridcs, but the amplitude and form of the light- 

 curves vary with the region of the spectrum observed. 

 Thus for '/3 Lyric the difference between the principal 

 maximum and minimum amounts to 0-66 magnitude with 

 the red, 0-94 magnitude with the green, and 1-34 magnitude 

 with the blue screen. The differences between the two prin- 

 cipal maxima vary from 0-3 magnitude with the blue to 

 zero with the red screen, and it is shown that this star 

 emits a greater proportion of the less refrangible rays_ at 

 the principal than at the secondary minimum. Similar 

 results accrue from the observations of 5 Cephei {Complcs 

 rendits, No. 10, p. 518, March 9). 



