August 29, 1895] 



NA TURE 



425 



temperature and physical conditions, arrangements were made 

 to photograph the spectra of stars and nebula;, in order to test 

 the view, employing a quite new basis of facts ; this new basis of 

 the inquiry consists of 443 photographs of 171 of the brighter 

 stars. 



Having this new and accurate basis of induction, the objects 

 were to determine whether the hypothesis founded on eye ob- 

 servations is also demanded by the photographs, and in the 

 affirmative case to discover and apply new tests of its validity, or 

 otherwise. 



The results as yet obtained are not sufficient to permit a dis- 

 cussion of all |)oints bearing upon the new classification, but 

 most of the crucial ones are certainly covered by the photographs 

 already obtained. 



The main instrument employed in the work has been a 6-inch 

 refracting telescope, with an object-glass made and corrected for 

 G by the Brothers Henry. This was at first used in conjunction 



with a prism of 7i° of dense glass by Hilger. The object-glass 

 and prism are fixed at the end of a wooden tube, which is at- 

 tached to the side of the lo-inch equatorial, at such an angle that 

 the spectrum of a star falls on the middle of the photographic 

 plate when its image is at the centre of the field of the larger in- 

 strument. The camera is arranged to lake plates of the ordinary 

 commercial size, 4I ;< 3J inches. The spectra obtained with 

 this instrument are o'6 inch long from F to K. .\n excellent 

 photograph of the spectrum of a first magnitude star can be ob- 

 tained with an exposure of five minutes. Afterwards a 6-inch 

 prism, with a refracting angle of 45°, obtained from the brothers 

 Henry, was used with the Henry 6-inch object glass. The spectra 

 obtained with the latter are two inches long from F to K, and 

 tne definition is exquisite. In some photographs the calcium 

 line at II is very clearly separated from the line of hydrogen, 

 which occupies very nearly the same position. It is unnecessary 

 to swing the bark of the camera in order to get a perfect focus 

 from F to K. The deviation of the jirism is so great that it 

 w ould be verj- inconvenient to incline the tube which supports it at 



NO. 1348, VOL. 52] 



the proper angle to the larger telescope. When photographing 

 the spectrum of a star, therefore, the star is first brought to the 

 centre of the field of the large telescope, and the proper des-ia- 

 tion is then given by reading off on the declination circle. This 

 method has been found to work quite satisfactorily. 



With this combination the exposure required for a first magni- 

 tude star is about twenty minutes. The method of mounting 

 the prism is shown in Fig. 41. 



For the fainter stars, the 6-inch prism of 7i° has been adapted 

 to a Dallmeyer rectilinear lens of 6 inches aperture and 48 inches 

 focal length. At times prisms of 7i° have been used on a 

 lo-inch equatorial. 



Since the spectrum of a point of light such as a star is a line 

 so fine that the spectral lines would not be measurable, it is 

 necessary to give it breadth. This is done by adjusting the 

 prism so that the spectrum lies along a meridian of R.A. and 

 altering the rate of the clock. 



J. NORM.\N LOCKYER. 



( To he continued. ) 



THE IRON AND STEEL INSTITUTE. 



T^HE annual suminer meeting of the Iron and Steel Institute 

 was held in Birmingham last week, commencing Tuesday, 

 the 20th inst. , and extending over Friday, the 23rd inst. Sir 

 David Dale, the President, took the chair at the sittings for the 

 reading of papers, and it may be said here that the meeting was 

 remarkably successful throughout, being one of the pleasantest 

 and most instructive gatherings that has been held for a long 

 time past ; both .Mr. Brough, the Secretar)' of the Institute, and 

 the local committee are to be congratulated on the excellence of 

 their arrangements. 



There were twelve papers down for reading and discussion, of 

 which the following is a list : — 



" On the Direct PuddUng of Iron," by E. Bonehill (.Mar- 

 chienne-au-Pont, Belgium). 



" On the Production of Iron by a New Process," by R. A. 

 Hadfield, member of Council (Sheffield). 



'■f)n the Thermo-Chemistrv of the Bessemer Process," by 

 Prof W. N. Hartley, F.R.S. (Dublin). 



" On the Hardening of Steel," by H. M. Howe (Boston, 

 U.S.A.). 



"On the Mineral Resources of South Staffordshire," by 

 II. W. Hughes (Dudley). 



" On the Iron Industry of South Staffordshire," by D. Jones, 

 Secretary of the South Staffordshire Ironmasters' Association 

 iShifnal). 



"On the Iron Industry of the South of Russia," by George 

 Kamensky (St. Petersburg). 



" On Cooling Curves and Tests of Cast Iron," by W. J. 

 Keep (Detroit, U.S. .A.). 



" On the Analysis of Ferro-Chromium," by E. H. Saniter 

 W'igan). 



" On Small Cast Ingots," by R. Smith-Casson (Birmingham). 



" On Tests of Cast Iron," by T. D. West (Sharpsville, Penn- 

 sylvania). 



"On Nickel Steel," by H. A. Wiggin (Birmingham). 



The papers of Mr. West and Mr. Keep were taken as read, 

 all the others being read and discussed. 



(Jn the members assembling on Tuesday morning, in the 

 Council House of Birmingham Corporation, they were welcomed 

 by the Mayor, and by the members of the local reception 

 committee. 



The first paper taken was that by Mr. D. Jones, on the iron 

 industry of South Staffordshire. This was an interesting con- 

 tribution, but mainly historical in its char.acter. It dealt with 

 the rise and progress of the iron industry of the district from its 

 earliest days, and, in treating of more modern times, pointed out 

 how the production of wrought-iron had decreased as steel had 

 taken its place, although a good deal of puddled iron is still 

 produced in the district. The paper of Mr. Hughes, on the 

 mineral resources of South Staffordshire, was very much of the 

 same character, and gave, in a convenient form, many facts 

 relating to the subject. 



.M. Bonehill's paper on the direct puddling of iron was next 

 read. This |)rocess appears to be a revival of, and doubtless 

 an improvement on, a method of puddling which was proposed, 

 and to a limited extent carried out, in the earlier years of the 

 century, but which never obtained any great hold in the iron 



