Al'RIL II, 1895J 



NA TURE 



561 



probably adopt a plan which has been extensively em- 

 ployed by Prof. Pickering, but so far has had few 

 imitators. This consists in photographing the trail of a 

 star. If we leave a phototelescope at rest with a plate 

 exposed, the stars describe circular arcs on the plate 

 having the pole as a centre, and having a length of 15" 

 for each hour of exposure. The lineir length will vary 

 according as the star is near or remote from the equator, 

 and since the energy is distributed over this varying 

 length, polar stars will produce more intense trails than 

 those stars of equal brightness near the equator. Kffec- 

 tively if two stars are found giving trails of equal den- 

 sity, the brightness of the two stars varies as the cosine 

 of the declination. But if it be found that the stars 

 near the equator travel, by reason of the earth's rotation, 

 so rapidly across the plate that the fainter among them 

 leave no trail, it is possible to give such a rate to the 

 driving clock that the trail may be of any definite 

 length, and the energy concentrated for a longer or 

 shorter time over this space. 



The method of deriving the stellar magnitude from an 

 examination or measurement of these trails will be best 

 understood by considering the case of the polar stars. 

 A plate was exposed to the pole for ten minutes, and the 

 telescope left stationary. The aperture was then reduced 

 by successive amounts, so that theoretically any star 

 would appear one magnitude fainter. In the case of a 

 selected star, therefore, we have the thickness of the 

 trail corresponding to known magnitudes, which could 

 at once be compared with the trails formed on other 

 plates. Actually these trails, corresponding, it is pre- 

 sumed, to stars of known magnitudes, were brought into 

 juxtaposition with the trails of stars whose magnitude 

 was sought, and the brilliancy was decided by equality 

 of appearance. Of course similar practices could be 

 and have been pursued when the stars are represented 

 on the plate by means of circular discs. By varying 

 the length of exposure in the photograph of a star of 

 known magnitude, we can approximate to the appear- 

 ance that stars of any magnitude would present for 

 known durations of exposure. But here difficulties con- 

 nected with the sensitiveness of the plate, and the 

 meteorological circumstances of the night affecting tlie 

 transparency of the atmosphere, have to be taken into 

 the account, and the effects eliminated from the obser- 

 vation as carefully as possible, so that it is doubtful if 

 a higher degree of precision results than in the case 

 of photometric observation. There is, however, the 

 obvious advantage that the photographs remain, and 

 greater leisure and further experiment may suggest 

 improved meihods of observation and reduction, that 

 shall ultimately give us all the accuracy needed in inves- 

 tigations of this character. The process as at present 

 employed by Prof. Pickering appears to be fairly rapid. 

 Three or four years ago he could report that he had 

 applied his method to over 60,000 images, and the 

 accuracy appears to be about as great as in the case of 

 photometric observations. The chances of systematic 

 error are probably greater. 



NOTES. 

 At Marlborough House, on Tuesday, in the presence of the 

 Council of the Society of .Vrts, the Prince of Wales presented 

 to Sir Joseph Lister, Bart., ihe Albert Midal accorded to him 

 by the Society for " The discovery and esiablishment of the 

 antiseptic method of treating wounds and injuries, by which not 

 only has the art of surijery been greatly promoted and human 

 life saved in all parts of the world, but extensive industries 

 have also been created for the supply of materials required for 

 carrying the treatment into effect." 



NO. 1328, VOL. 51] 



Prof. Christopher Heath has been elected President of 

 the Royal College of Surgeons, in the place of the late Mr. J. 

 Whitaker Hulke, F.R.S. 



Dr. G. S. Buchanan has been appointed to the office of 

 Medical Inspector of the Local Government Board. 



The Croonian Lectures at the Royal College of Physicians 

 will be delivered by Dr. W. Marcet, F. R. S., on June l8, 20, 

 25, and 27, the subject being the " Respiration of Man." 



The grants lately made by the United States Congres.=, for 

 the Geological Survey during the fiscal year iS95-t;5, amount to 

 515,000 dollars, or ;^io3,ooo. This sum includes all field and 

 office expenses and salaries. 



L.A.ST week, the colleagues and former pupils of Sir William 

 Turner, Professoi of Anatomy in the University of Edinburgh, 

 presented him with his portrait, ai a mark of appreciation of 

 his services in the cause of science and to the University. 



In connection with the Goldsiniihi' Company's grant for 

 researches on the anti-toxin treatment, a Committee of the 

 Royal College of Surgeons of England have recommended a 

 grant of one hundred pounds to Dr. Sidney Martin, for the 

 purpose of working out the action of the ami toxic serum, 

 when used to counteract the effects of various poisons 

 separated by him from the membrane, and from the spleen, in 

 cases of diphtheria. 



We have already noted that the London Chamber of Com- 

 merce are promoting a Bill for legalising the use of metric 

 weights and measures for export trade purposes. In connection 

 with this, the London County Council has just res jIved to do 

 all in its power to secure the passing of the Bill during the 

 present Session. In the meantime the Council's inspectors 

 will not interfere with the use of metric weights and measures 

 in the execution of foreign order.-. 



Among the men of science who have died during the past 

 week is Iheodor Brorsen, whose name is so well known to 

 astronomers. He was born in 1S19, and was the discoverer of 

 five comets, as well as the author of a number of writings on 

 astronomical subjects. Since 1879, he lived in retirement at 

 Norburg, his native place. Mr. J. H. Greener, the constructor 

 of several early lines for telegraphic communication, and one 

 of the most able of practical telegraph engineers, died on 

 Sunday, in his sixty- sixth year. 



The President of the German Meteorological Society has 

 issued invitations for a general meeting of the Society, to be 

 held at Bremen on the lyih, i8th, and 19th inst., when various 

 matters of interest to meteorologists will be discussed. The 

 time of meeting has been tixed so as to fall in with the geo- 

 graphical conference, which will be held at the same place 

 during Easter week, and in which oceanography and maritime 

 meteorology form a prominent part. Tlie subject of south 

 polar investigation is also included in the geographical pro- 

 gramme, so that it is anticipated that a large number of scien- 

 tific men will lake part in the proceedings. 



The spring meeting of the Iron and Steel Institute will be 

 held in London on Thursday and Friday, May 9 and 10 next, 

 in the rooms of the Society of Arts. The presidential address 

 will be delivered by Mr. David Dale, and the Bessemer gold 

 medal will be awarded to Mr. H. M. Howe, who will contri- 

 l.ute a paper on "The Hardening of Steel." Mr. Stead, of 

 Middlesbrough, will contribute a paper on " The Effect of 

 Ar^enic on Steel"; Mr. Sergius Kern, Metallurgist to the 

 Russian Admiralty, will discuss the manufacture of armour- 



