Ma^ 24, 1906] 



NA TURE 



«7 



I'roi-. R. Walter states in a brief note publishr-d in tin- 

 AnnaU-n (h-r Physik (vol. xix., p. 874) that the ultra-violil 

 portion of the spectrum of a high-tension arc in air shows 

 a series of hands identical with those observed by Eder 

 in i8q2 as characterising the combustion of ammonia, and 

 considered by him as ammonia bands. It would appear 

 probable that these bands are to be attributed rather Ki 

 an oxide of nitrogen, produced in both cases, than to ihc 

 cause suggested by Eder. 



.So.ME successful attempts, made in the geophysical labor- 

 atory of the Carnegie Institution, to prepare small plates 

 of quartz glass suitable for the construction of lenses, 

 mirrors, or other optical apparatus, are described by 

 Messrs. .Arthur L. Day and E. S. Shepherd in Science 

 (vol. xxiii.. No. 591). The glass obtained was nearly free 

 from air bubbles, and was only slightly discoloured by the 

 presence of silicon. The conditions for obtaining such a 

 material by the fusion, in a small graphite box, of pure 

 crystallised quartz or tridymite, are summarised as 

 follows : — an initial temperature of 2000° or more without 

 pressure, so as to allow of the production of sufficient 

 vapour to drive out the air betw-een the grains, followed 

 by pressure (at least 500 lb.) and a reduced temperature 

 of about iSoo°, with time for the quartz to flow" compactly 

 together w'ithout being attacked by the graphite. 



.An interesting contribution to the study of fluorescence 

 is contained in a paper published by Mr. Harry \V. Morse 

 in the Proceedings of the American Academy of Arts and 

 Sciences (vol. xli.. No. 27) under the title " Studies of 

 Fluorite. " The fluorescence and thermoluminescence of 

 fluorite and the nature of the gaseous and liquid in- 

 clusions in fluorspar are dealt with under different head- 

 ings. The fluorescence spectra shown by fluorite when 

 e.xcited by the light of the condensed electric spark between 

 electrodes of certain metals contain sharp lines and narrow 

 bands ; the lines of these fluorescence spectra do not appear 

 to belong to any known substance, and are remarkable 

 inasmuch as different lines are obtained with different 

 exciting sources. The spectrum also varies sharply from 

 crystal to crystal with the same means of excitement. The 

 cause of fluorescence, whatever be its nature, is removed 

 or destroyed by heating at a temperature of about 300° C. 

 At the same temperature the colouring matter of the 

 difl'erent varieties of fluorite is destroyed ; the nature of 

 this colouring matter is discussed by reference to the 

 gaseous products liberated at higher temperatures. .As 

 these consist of hydrogen, carbon monoxide, and carbon 

 dioxide, the colouring matter W'ould appear to be organic 

 in its origin; the gases are probably produced by its under- 

 going a process of destructive distillation 



No. 3, vol. xxiii., of the Astrophysical Journal contains 

 an important paper by Mr. Theodore Lyman on the extreme 

 ultra-violet spectrum of hydrogen. Part of this spectrum 

 was previously photographed and investigated by Dr. 

 Schumann, whose w-ork was briefly described in vol. Ixix. 

 (p. 262) of Nature. Unfortunately Dr. Schumann, 

 although he photographed the spectrum down to \ 1270, 

 was unable to give the wave-lengths beyond X 1850, but 

 this omission has now been rectified by Mr. Lyman, who 

 has not only determined the missing wave-lengths, but has 

 also extended the known spectrum down to \ 1030 (see 

 Natlre, p. 465, vol. Ixix., and p. no, vol. Ixx.). In the 

 present paper the author describes the apparatus and 

 methods employed in great detail, " in the hope that an 

 exact knowledge of the conditions necessary to success 

 may prove of value to investigators who work in this 



NO. 1908, VOL. 74] 



firld " ; he also gives reproductions of his spectrograms, 

 with wave-length scales, for the region between A 1670 

 and A 1270. 



The W'atkins Meter Co., Hereford, has published a third 

 edition of " The W'atkins Manual of Exposure and Develop- 

 nicnl." by Mr, .Alfred Watkins. 



The report for the year 1905 of the council of the Hamp- 

 stead Scientific Society has been received. The Christmas 

 juvenile lectures, and those on nature-study, intended to 

 encourage the teaching of this subject to children, proved 

 very successful. Among lectures delivered at the general 

 meetings of the society may be mentioned those by Prof. 

 Marcus Hartog, on the end and beginning of individuality 

 as shown in the living cell ; Dr. R. S. Clay, on the peculi- 

 arities and paradoxes of fluid pressure ; Sir Samuel Wilks, 

 F.R.S., on spirals; Dr. C. \V. Andrews, F.R.S., on fossil 

 hunting in the Libyan Desert ; and Mr. F. W. Rudler, on the 

 geology and scenery of the British Isles. 



The seventy-second annual report of Bootham School 

 (York) Natural History, Literary, and Polytechnic Society 

 shows that the pupils of this school continue to receive 

 every encouragement to devote their leisure hours to the 

 outdoor study of natural phenomena. During 1905 the 

 boys were particularly successful in discovering rare plants, 

 and though we have been unable to find a specific caution 

 in the report, we trust that all observers are urged not 

 to uproot plants or in any other way to assist the dis- 

 appearance of rare species. It is satisfactory to find that 

 attention is given to many branches of natural science so 

 that the predilections of as many boys as possible may be 

 satisfied. 



OUR ASTRONOMICAL COLUMN. 



Spectrum of Nova Aquil^ No. 2. — .A visual observation 

 of the spectrum of Nova Aquil^ No. 2, made at the Lick 

 Observatory on September 5, 1905, showed a number of 

 bands, the brightest of which was recognised as H^. 

 H7 and a band near A 4600 were distinguished with 

 difficulty owing to their extreme faintness. 



Photographs obtained with the one-prism spectrograph 

 on September 6 and 10 (exposures three and four hours 

 respectively) confirmed the visual observation, the intensi- 

 ties of the' bands at A 4600 and H7 being respectively one- 

 fifth and one-tenth that of H/3. H5 was also seen, but 

 was very faint. 



.A faint continuous spectrum was seen to extend from 

 about A 4500 to the region of the H7 band. He and the 

 so-called nebular lines were not visible. 



Visual and photographic observations made on October 

 II, 1905, agreed in showing a marked diminution in the 

 brightness of HB, which was then no brighter than H7 

 {Astrophysical Journal, vol. xxiii.. No. 3). 



A number of magnitude observations of this Nova, made 

 on various dates between September 20 and November 24 

 at the Utrecht Observatory, are recorded in No. 4089 of 

 the Astronomische Nachrichien by Dr. A. A. Nijland. 



STEREO-COMPAR.'iTOR DISCOVERIES OF PROPER MOTIONS. — 



At a meeting of the Paris Academy of Sciences, held on 

 Mav 7, Prof. Loewy announced that Prof. Max Wolf had 

 met with considerable success in discovering and measur- 

 ing stellar proper motions by means of his stereo- 

 comparator. 



In one instance a star of known proper motion was seen 

 to be obviously displaced after the very short interval of 

 four years. When the two photographs, taken at this 

 interval, were placed in the stereoscope, the star in ques- 

 tion was seen to stand out in a plane considerably different 

 from that in which the neighbouring stars appeared to be 

 set. 



Prof. Wolf has also been able to show that a ninth- 

 magnitude star in the constellation Leo has a proper 



