Maech 13, 1896.] 



SCIENCE. 



401 



hitherto fallen upon the generous Trustees from 

 Boston and their friends, not only by the aid of 

 the thirty cooperating colleges, but by the 

 formation of the 'Biological Association,' the 

 chief object of which is to aid the Laboratory 

 in securing funds necessary to the foundation of 

 a biological station as a National center of re- 

 search in every department of biology. Local 

 committees have also been formed, such as 

 those in New York and Philadelphia." 



During the year a large number of evening 

 lectures were given by well-known morpholo- 

 gists and physicists, and the daily morning lec- 

 turers include a very large number of well- 

 known names. Besides this, there has been 

 regular instruction in vertebrate and invei-te- 

 brate morphology and a course in embrj^ology. 



THE EONTGEN EAYS. 



Some twenty papers on the Rontgen rays 

 have already been presented before the Paris 

 Academy of Sciences. On February 10th M. 

 C Henry reported that coins coated with phos- 

 phorescent zinc sulphide lose their opacity to 

 the rays. Nature thus summarizes the papers 

 presented on February 17th : "In following up 

 the analogy of certain properties of these rays 

 with some properties of the ultra-violet rays, 

 M. E. Swyngedauw has found that the X-rays 

 cause a lowering of the explosive potential ac- 

 cording to the same general laws as the electri- 

 cally active ultra violet rays. Whilst the in- 

 fluence of the latter, however, is entirely sup- 

 pressed by interposing a screen of wood, glass 

 or blackened paper, these materials do not 

 effect this property of the Rontgen rays. It 

 was also noticed tliat 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. Eighi 

 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. 

 Bergman 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 re- 

 duction of angle between the leaves of an elec- 

 troscope 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 coefficient of transmission 

 (0.85) of an aluminium plate, 0.1 mm. thick, 

 it is shown that a plate of aluminium 15 mm. 

 thick, such as was used by Rontgen in his orig- 

 inal experiments, must be practically opaque to 

 the rays unless the rays are heterogeneous. In an 

 extract from a letter by de Heen an ingenious 

 experiment is described which proves conclu- 

 sively that the X-rays proceed from the anode, 

 and not the cathode. A leaden plate perforated 

 with holes is placed Tjetween the Crookes' tube 

 and the photographic plates, and the direction 

 of the bundles of rays obtained shows clearly 

 that these rays are anodic. 



ASTRONOMY. 



The Munich Observatory has just issued a 

 very elaborate investigation of astronomical 

 refraction from meridian circle observations 

 made for this special purpose by Dr. Julius 

 Bauschinger. The instrument used was the 

 new six-inch, which was set up towards the 

 end of 1891. The present series of observa- 

 tions are therefore the first ones made with 

 this instrument. The method employed was 

 the usual one of comparing the declinations oi 

 the same star obtained at the upper and lower 

 culmination. The paper as a whole impresses 

 one with the extraordinary care and thorough- 

 ness with which every part of the work has 

 been done. We can, of course, only touch very 

 briefly upon a few points that appear of special 

 interest. 



No corrections for errors of the microscopes, 

 errors of division of the circle, or flexure of 

 the tube, were applied to the observations, as 

 very careful investigation of all these matters 

 showed that the existence of such errors was 

 not established with certainty. This speaks 

 very highly for the skill of the instrument 



