May i8, 191 i] 



NATURE 



393 



coefficient of one single term occupies eight pages. More 

 e-^pecial attention is paid to the two standard positions of 

 Gauss and the two standard positions of Lamont. These 

 have been treated with more or less completeness by 

 several previous magneticians, amongst whom Lamont and 

 Borgen are specialh' mentioned ; but, according to Leyst. 

 few if any of his predecessors who have given formulae for 

 all four cases have wholly escaped printers' errors. Ex- 

 pression is given to the belief that the differences between 



•^sults obtained for the horizontal component of the earth's 



nagnetic force with different magnetometers are due in 

 large measure to insufficiency in the deflection formula; 



■inployed. There seems, however, no reference to the 

 : lieoretical or experimental work on this question carried 



ait of late \ears in this country and in India. 



The Electrician for April 14 contains an abstract of the 

 ! ist three of Sir J. J. Thomson's Royal Institution lectures 

 in radiant energy and matter. They dealt with the dis- 

 ribution of energy in the spectrum of a black body, the 

 relation between radiation and absorption of a body, the 

 character of the absorption of gases, and the nature of 

 radiation and of light waves. The same number of The 

 Electrician contains a summary of the lecture on the 

 deflection of the positive rays of the vacuum tube as a 

 new means of chemical analysis. Since the ratio of the 

 deflections of a particle in the electric and magnetic fields 

 depends on the quotient of the electric charge carried by 

 the mass of the particle, an examination of the deflections 

 allows some deductions to be made as to the composition 

 and charges of the particles. Oxygen, for instance, 

 appears to exist in the tube in nine modifications, and 

 these help us to understand why the same chemical sub- 

 stance is so often capable of giving entirely different spectra 

 under different conditions. 



The illuminating engineers of America appear to have 

 commenced a crusade against the evil of " glare " in 

 artificial illumination, and the subject is given a prominent 

 place in several of the Aijaerican scientific journals. Tlie 

 Scientific American for April 15 contains an article on light 

 and shadows ministering to eye comfort, by Mr. E. C. 

 Chittenden, of the Bureau of Standards. He considers 

 tliat the present method of lighting large rooms by lamps 

 concealed in recesses close to the ceiling gives too great 

 uniformity of illumination to be pleasamt to the eye, and 

 prefers visible lamp fixtures provided with fittings of prism 

 glass, which send the light in the direction required. 

 According to the April number of The Illuniinatinfl 

 Engineer of New York, an American Association for the 

 Conservation of Vision has been formed, and the editor 

 sums up a few of the questions at issue as follows : — 

 (i) Is glare so injurious to the eyes as is generally 

 believed? (2) Is indirect lighting good or bad? (3) Is the 

 Cooper-Hewitt lamp injurious to the eyes? 



A suiTLE.MENT to The Electrician of May 12 devotes 



! nearly 200 pages to special articles an the present position 



[of electric power in mining. Since the corresponding 



'supplement was issued three years ago, new rules have 



been issued by the Home Office dealing with the use of 



[electrical appliances in mines, and one of the articles is 



devoted to the elimination of risk from explosion and from 



shock in the use of electricity. Other articles deal with 



Lthe supply of power, either from a public or from a private 



station to the colliery, the winding plant, the wiring of 



the mine, coal-cutting machinery, haulage plant, pumps, 



switches, and electric hand lamps; Each is written by a 



man well quafified to deal with his subject, e.g. Prof. 



NO. 2 1 68, VOL. 86] 



W. M. Thornton, Mr. H. J. S. H^-ith^r. and Mr. W. B. 

 Siiaw. 



Messrs. Negretti and Zambra have submitted to us a 

 pair of folding prismatic binoculars, which we have care- 

 fully tested. The chief feature is the manner in which 

 the binoculars may be folded for ease in carrying to fit 

 into a case 35 inches wide and only one inch thick. This 

 is achieved by mounting the prism in which the first two 

 reflections occur separately from the prism producing the 

 last pair of the four reflections of the usual prismatic 

 system. This has not resulted in any sacrifice either in 

 power, aperture, or — so far as we can see — in illumina- 

 tion. We have ascertained that the magnification and field 

 of view as given by the makers, viz. 5-5 diameters and 

 8-3°, are approximately correct, and these compare very well 

 with the ordinary prism-binocular. The focussing is 

 smooth, the introcular distance can be adjusted, and for a 

 small range the focus can be separately adjusted for each 

 eye. The only criticism we have is of the spring catches 

 which hold it in position for use, which do not appear 

 quite strong enough. Incidentally, the glasses provide very 

 interesting evidence of the power we possess of rotating 

 our eyes in their sockets (by means of the oblique muscles). 

 If the spring catches are released while looking through 

 the glasses, and the bodies are slightly rotated, as in fold- 

 ing them, the images seen by the two eyes rotate in 

 opposite directions. It will be found that for a few degrees 

 either way the eyes are able to follow, and to fuse the 

 images into one. 



In the paragraph on a fresh-water rhizocephalan in our 

 last week's issue, the Records of the Indian Museum is 

 quoted as Records of the British Museum. 



OUR ASTRONOMICAL COLUMN. 



The Bright Meteor of April 30. — Mr. Harrison Hill, 

 of .Abbey Road, N.W., writes to say that he also observed 

 the brilliant meteor which was seen, as reported in these 

 columns last week, by the Rev. T. E. R. Phillips. At 

 midnight on .April 30 Mr. Hill's attention was arrested by 

 a sudden and bright light, which appeared to be a large 

 star, in the S.W. sky. This object increased rapidly in 

 size and apparent brightness, and then disappeared. 

 Although Mr. Hill has frequently observed " shooting 

 stars," this meteor especially impressed him by reason of 

 its lack of apparent motion and its exceeding brightness. 



The Spectrum of Nova Lacert.^. — .\ comprehensive 

 study of the spectrum of Nova Lacert.-v is published in 

 No. 194 of the Lick Observatory Bulletins by Prof. \V. H. 

 Wright. Spectrograms were secured early in January with 

 spectrographs attached to the 36-inch and 12-inch refractors, 

 but subsequent observations were prevented by a protracted 

 storm which set in after January 6. Altogether, some 140 

 wave-lengths are given as positions of lines, or as maxima, 

 minima, or limits of bands. .As remarked by Prof. Wright, 

 the interpretation of this complex structure of the spectrum 

 is a difficult problem in which great caution must be used. 

 There is one point to which he directs specific attention, 

 however. In the comparison iron-spark spectrum the air 

 lines appear as usual, and show a large measure of agree 

 ment with many of the bright-band maxima in the star 

 This is shown by a table comparing the nitrtigen wave 

 lengths given by Exner and Haschek and Neovius with 

 the stellar wave-lengths. But it should be noted that the 

 strongest nitrogen line, \ 3995, is absent from the star 

 spectrum, as are also some of the fainter lines in the 

 spectrum of the gas ; neglecting the lines of intensity two 

 and less, there is, however, a striking agreement except for 

 some discrepancies in wave-length such as might easily 

 occur in the measures of the involved nova spectrum. This 

 is interesting and suggestive, but, as Prof. Wright says. 



