February 27, 1896] 



NA TURE 



399 



obtaining a photograph of a key, covered by a board, by five hours' 

 exposure to direct sunlight. Elaborate experiments are in pro- 

 gress at Columbia, under the direction of Profs. Rood, Papin, 

 and Hallock, with a prospect of important results." 



With reference to the report that Prof. Salvioni had dis- 

 covered how to make directly visible the bones of the hand by 

 means of Rontgen rays, the Rome correspondent of the British 

 Medical Journal says :— " At a meeting of the Perugia Medico- 

 Chirurgical Society, held on February 5, Prof. Salvioni, 

 teacher of physics at the University, made a most important 

 communication on the new results obtained by him in Rbntgen's 

 rays. In studying the question, his aim was to invent an 

 apparatus which would enable one to see direct and without 

 the intervention of photography certain bodies enclosed in 

 wood, flesh, cardboard, &c. He therefore studied the possi- 

 bility of rendering the retina sensitive to Rontgen's rays. In 

 thi^ he has succeeded by inventing an apparatus which he has 

 called a cryptoscope, which he exhibited at the meeting, and 

 by means of which one can clearly see the contours of the 

 bones of one's own hand, objects enclosed in cardboard boxes, 

 leather purses, &c. This apparatus is very simple, and consists 

 of a black cardboard tube enclosed at one end with a disc of 

 black cardboard coated internally with a fluorescent substance 

 (barium platino-cyanide, sulphate of calcium, &c.) ; in the other 

 end is placed a lens which permits one to clearly see the 

 fluorescent surface. The object to be observed is placed before 

 the luminous source given by a Crookes' tube, and then one 

 looks at it through the cryptoscope placed at a suitable distance. 

 As in the fluorescent cardboard the parts of the object im- 

 permeable to Rontgen's rays are drawn in shadow, thus one 

 clearly sees the contours of the bones of the hand, &c. A 

 luoilel of the instrument was made under the direction of Prof. 

 l)lasema at the Physical Cabinet of the Roman University on 

 February 11, and with it one could clearly see the bones of 

 one's own hand, coins in a purse or the clenched hand, &c. It 

 is evident from these results that the apparatus, when perfected, 

 will be of great use in medicine and surgery.'" 



The current number of the Comptes rendus contains no less 

 than seven papers bearing on the Rontgen rays. In following 

 n\\ the analogy of certain properties of these rays with some 

 properties of the ultra-violet rays, M. R. Swyngedauw has 

 lound that the X-rays cause a lowering of the explosive poten- 

 tial according to the same general laws as the electrically active 

 ultra-violet rays. Whilst the influence of the latter, however, is 

 entirely suppressed by interposing a screen of wood, glass, or 

 blackened paper, these materials do not affect this property of the 

 Rontgen rays. It was also noticed that these rays lowered the 

 dynamic explosive potentials to a greater extent than the static 

 potentials. As a result of the study of the property of the Rontgen 

 rays of discharging an electrified body, M. A. Righi concludes 

 that the time necessary for a given fall of potential is 

 practically the same, whether the original charge be positive 

 or negative. With an initial positive charge the discharge 

 is not complete ; but if negative initially, not only is 

 the discharge complete, but the disc becomes positive. 

 The results obtained by MM. J. J. Borgman and A. L. Gerchun, 

 however, are precisely contrary to these, a positively charged disc 

 losing its charge nearly instantaneously, and becoming negative 

 on prolonged exposure to a Crookes' tube. MM. L. Benoist 

 and D. Hurmuzescu contribute further researches on the same 

 subject of a quantitative character. By measuring the time 

 required for a given reduction of angle between the leaves of 

 an electroscope, and the distance of the leaves from the Crookes' 

 tube, they prove that the ratio of the times are as the ratio of 

 the squares of the distances. From the coefiicient of trans- 

 mission (o"85) of an aluminium plate, O'l mm. thick, it is 

 NO. 1374. VOL. 53] 



shown that a plate of aluminium 15 mm. thick, such as was 

 used by Rontgen in his original experiments, must be practically 

 opaque to the rays unless the rays are heterogeneous. In an 

 extract from a letter by M. de Heen, an ingenious experiment is 

 described which proves conclusively that the X-rays proceed 

 from the anode, and not the kathode. A leaden plate perforated 

 with holes is placed between the Crookes' tube and the photo- 

 graphic plates, and the direction of the bundles of rays thus 

 obtaiined shows clearly that these rays are anodic. 



Dr. M. Armand Ruffbr has resigned the post of Director 

 of the British Institute of Preventive Medicine, and has been 

 appointed Professor of Bacteriology at the Medical School of 

 Cairo, vice Dr. Kaufmann, resigned. 



Colonel C. F. Crocker, a member of the Regents' Com- 

 mittee of the Lick Observatory, has undertaken to pay the 

 expenses of an expedition which will be sent from the Observa- 

 tory to Japan to observe the forthcoming solar eclipse. The 

 expedition will be under the direction of Prof. Schaeberle, and 

 its programme will be wholly photographic. 



Charles Wachsmuth, well known as a palaeontologist in 

 the line of Crinoids, died suddenly at Burlington, Iowa, 

 February 17, aged sixty-six years. He was a native of 

 Germany, and had spent forty years in scientific research among 

 the Crinoids of the Mississippi Valley and the Tennessee 

 Mountains. 



The deaths are announced of Prof. J. Graindorge, Professor 

 of Mathematical Physics and Kinematics at LUttich ; M, Abel 

 Hovelacque, the distinguished Anthropologist and Orientalist, at 

 Paris ; Dr. K. Stolzel, Professor of Technical Chemistry and 

 Metallurgy in the Technical High School at Munich ; Dr. P. 

 Hedenius, Professor of Pathology and Pathological Anatomy 

 at Upsala. 



The progress in electric propulsion appears in many ways. 

 Electric motors have been tried and will be substituted for steam 

 on the New York and Brooklyn Bridge as a means of switching 

 trains at the termini, thus practically doubling the capacity of the 

 bridge. A Westinghouse system railroad locomotive, the first one 

 constructed, has just been completed at Philadelphia, and sent 

 to Pittsburgh for its electric equipment. A speed of 200 miles 

 an hour is claimed. Experiments indicate that electricity will 

 soon supplant steam as a motor on the entire New York 

 elevated railroad system. 



The following prizes have recently been awarded by the 

 Academic Royale de Belgique : M. J. Verschaffelt, 600 francs for 

 his work on the determination of molecular weights of bodies in 

 solution ; M. E. Haerens, 1420 francs (Prix Charles Lemaire) 

 for the best treatise on public works. The following have been 

 elected Foreign Associates of the Academy: Profs. Sylvester 

 (Oxford), Cannizzaro (Rome), Strasburger (Bonn), Cope (Phila- 

 delphia), M. Marey (Paris), and Sir Archibald Geikie (London). 

 M. F'raipont (Liege) has been elected Correspondant in the 

 Natural Science Section. 



All who are working for the reform of our system of weights 

 and measures will be interested to know that the Swiss Govern- 

 ment have recently invited the countries parties to the Berne 

 Convention — in other words, all the leading countries of the 

 continent of Europe— to a conference to discuss inter alia the 

 introduction of a uniform gauge of screws based on the metric 

 system. Mr. W, M. Acworth remarks in the Times that, 

 according to the official document, this gauge is intended to take 

 the place of the " so-called Whitworth system, based on Eng- 

 lish measures, which is at present in use under various forms. " 

 It is pointed out that there is an immense advantage in having 

 the material for the repair of rolling-stock, which often travels 



