May 22, 1896.] 



SCIENCE. 



783 



The solid state of the coal is analogous to the 

 similar state of the slate in the small quarry- 

 near Siegfried, where workable slate is quarried 

 immediately under glacial gravel. Both are on 

 the line of farthest ice extension — of earliest 

 extension — and speak of its recency. 



Edward H. Williams, Jr. 

 Lehigh Univeesity, 



May 11, 1896. 



A METEOR. 



To THE Editor of Science: A few days 

 ago I observed a meteor of such size as ap- 

 parently to merit record. At 7:30 p. m. of May 

 9th the object was first seen in the twilight 

 descending in a straight course toward the 

 northwest at an angle of about 20° with the 

 plane of the horizon, moving rather slowly and 

 shining brilliantly with a greenish light. It 

 very soon after burst into numerous fragments, 

 the position at rupture bearing about 30° west 

 of south from the end of the Norfolk and Wash- 

 ington steamboat pier at Alexandria, Va. , and 

 being at an elevation of about 10° above the 

 horizon. 



Thos. L. Casey. 



S-EAY photography BY MEANS OP THE 

 CAMERA. 



I HAVE recently succeeded in producing X- 

 ray pictures, reducing them in their linear di- 

 mensions to one-fifth the size of the object. 

 The method used was to produce on a tungstate 

 of calcium screen the shadows of the object, the 

 screen with its contents being then photo- 

 graphed by means of the camera in the ordi- 

 nary way. 



The photographs thus obtained reveal the 

 details more clearly than the eye can see them 

 on the screen, and, in fact, reveal details not 

 visible to the eye. 



There is some advantage in this method 

 over that usually employed. The photographic 

 plates may be made of reasonable size for large 

 objects. The pictures gain somewhat in defi- 

 nition, as penumbral effects are reduced. The 

 disadvantages are the difliculty of accurately 

 focussing the faint images on the ground glass 

 of the camera, and the longer time of exposure 

 needed to bring out the picture. I think it 



probable that these difficulties may not he very 

 serious to those possessing the best facilities for 

 making further study in this direction. 



Francis E. Nipher. 

 Washington Univeesity, 



St. Louis, May 11, 1896. 



THE ROTATING CATHODE. 



Since writing an account of my observation on 

 the rotation of the cathode disc (p. 750) it has 

 occurred to me that a circular or elliptical vibra- 

 tion of the cathode wire might possibly account 

 for the observed effect. The tube on which the 

 observation was made has been cracked, and 

 now ceases to give the result, nor am I able to 

 impart rotation in one direction only to the 

 disc by familiar mechanical means that could 

 have existed in the tube. The observation is 

 one of such great interest that I think I should 

 suggest the above possible explanation, which 

 had not sooner occurred to me, in order to pre- 

 vent experimenters from going on what may be 

 a wild-goose chase. Francis E. Nipher. 



May 13. 



SCIENTIFIC LITERATURE. 

 The Principles of Museum Administration. By 

 G. Brown Goode, LL. D. (Reprinted from 

 the Annual Report of the Museum Associa- 

 tion, 1895.) York, 1895. Pp. 73. 

 ' ' The degree of civilization to which any 

 nation, city, or province has attained, is best 

 shown by the character of its public museums 

 and the liberality with which they are main- 

 tained." The above sentence — the concluding- 

 sentence of the paper before us — sets forth in 

 striking phrase the importance of the subject 

 with which the paper deals. Superlatives are 

 in general things which a cautious man views 

 with suspicion, and it may well be doubted 

 whether any one index of the state of civiliza- 

 tion can be said to be the best. But that mu- 

 seums afford one of the most trustworthy indices 

 of the progress of civilization cannot be doubted. 

 The indication which they afi'ord is decidedly 

 flattering to our generation ; for this is certainly 

 preeminently the age of museums. In the 

 number of museums, large and small, general 

 and special, in the munificence with which they 

 are sustained and endowed, in the knowledge? 



