538 



SGIENGE. 



[N. S. Vol. III. No. 67. 



W. Gibbs, G. L. Goodale, H. B. Hill, C. L. 

 Jackson, E. C. Pickering, F. W. Putnam, 

 C. S. Sargent, J. Trowbridge. 



Chicago: The University of Chicago, (1): 

 A. A. Michelson, C. O. Whitman. 



College fii^L-Tufts College, (1) : A. Michael. 



Hoboken : Stevens Technological Institute, 

 (2): A. M. Maj'er ; H. Morton. 



New Haven: Yale University, (13) : W. 

 H. Brewer, G. J. Brush, R. H. Chit- 

 tenden, E. S. Dana, W. L. Elkin, J. W. 

 Gibbs, C. S. Hastings, S. W. Johnson, 0. 

 C. Marsh, H. A. Newton, S. I. Smith, A. 



E. Verrill, A. W. Wright. 



JVew York: American Museum, (1) : J. 

 A. Allen. 



iVew York: Columbia College, (3): C. 



F. Chandler [G. W. Hill], R. Mayo- 

 Smith, O. N. Rood. 



Neiv York: The Public Library ( — ) : [J. 

 S. Billings]. 



Philadeljohia : University of Pennsylvania, 



(4) : G. F. Barker [J. S. Billings], E. D. 

 Cope, J. P. Lesley, H. C. Wood. 



Princeton: College of ]S"ew Jersey (1): C. 

 A. Young. 



Providence: Brown University (2) : C. 

 Barus, A. S. Packard. 



Washington: U. S. Army, (5): H.L.Ab- 

 bot, J. S. Billings, C. B. Comstock, E. 

 Coues, C E. Dutton. 



Washington : American Ephemeris, ( — ) : 

 [G. W. Hill] , [S. Newcomb] . 



Washington: U. S. Navy, (2) : A. Hall, 

 S. Newcomb. 



Washington: U. S. Coast and Geodetic 

 Survey, (1) : C. A. Schott [H. Mitchell]. 



Washington: U. S. Geological Survey 



(5) : G. F. Emmons, G. K. GHbert, A. 

 Hague, R. Pumpelly, C. A. White. 



Washington : U. S. Weather Bureau, (1) : 

 C. Abbe. 



Washington : Smithsonian Institution and 

 National Museum and Fish Commission, 

 (4) : T. N. Gill, G. B. Goode, J. P. 

 Langley, J. W. Powell. 



Waterville: Colby Universitj', (1) : W- 

 A. Rogers. 



Worcester : Polytechnic Institute, (1) : T. 

 C. Mendenhall. 



In Private Life: (15) : A. G. Bell, S. C. 

 Chandler, B. A. Gould, G. W. Hill, C. 

 King, M. C. Lea, T. Lyman, H. Mitchell, 

 S. W. Mitchell, E. S. Morse, C. S. Pierce, 

 F. Rogers, S. H. Scudder, W. SeUers, J. H. 

 Trumbull. 



Edward S. Holden. 

 Lick Obskevatoey, 

 Umveesity of California. 



DIFFUSIVE REFLECTION OF EONTGEN BA Y8.* 

 The following communication contains a 

 brief description of a series of experiments 

 with Rontgen radiance which were con- 

 ducted during the last six weeks. The re- 

 sults of these experiments seem to possess 

 a suflBcient scientific and practical impor- 

 tance to merit notice. The most important 

 refer to diffuse reflection or scattering of 

 Rontgen radiance. It seems desirable to 

 state first, briefly, the disposition of the ap- 

 paratus and the method of experimenta- 

 tion by means of which the Rontgen effects 

 can be rendered sufficiently intense for the 

 purpose described below. 



Induction Coil and Interrupter. A pow- 

 erful coil was found indispensable for strong 

 effects and satisfactory work. The vibra- 

 ting interrupter is too slow and otherwise 

 unsatisfactoiy, and it was replaced by a ro- 

 tary interrupter, consisting of a brass pul- 

 ley, 6 inches in diameter and 1-|- inches in 

 thickness. A slab of slate f inch thick was 

 inserted and the circumference was kept 

 carefully polished. This pulley was mounted 

 on the shaft of a Crocker-Wheeler \ HP 

 motor giving 30 revolutions, and, therefore, 

 60 breaks per second. Two adjustable 

 Marshall condensers of three microfarads 

 each were connected in shunt with the break, 



* Presented before the New York Academy of Sci- 

 ences, April 6, 1896. 



