174 



SCIENCE. 



[N. S. Vol. XVII. No. 422. 



for the very briefest times of charge, while 

 a paraffine condenser may show a reduc- 

 tion in capacity of some sixty per cent, 

 from a time of charge of 0.4 second to 

 that of 0.001 second. 



Derivation of Equation of Decaying Sound 

 in- a Boom, and Definition of Open Win- 

 dow Equivalent of Absorbing Power of 

 the Boom: W. S. Fbanklin, Lehigh 

 University. 

 1. The paper presents a derivation of 



the equation 



in which I is the initial intensity of sound 

 in a room, i is the intensity t seconds after 

 the source has ceased, v is the volume of 

 the room, a is the open window area which 

 is equivalent to the absorbing power of 

 the wall and objects in the room, and ^ is 

 the Naperian base. 



2. The paper then gives a definition of 

 the open window equivalent of the ab- 

 sorbing power of the walls and objects in 

 a room. 



3. The paper then compares the theo- 

 retically derived equation for duration of 

 reverberation, namely, 



?, =0.165-, 

 a 



with the equation used by Sabine in which 

 the numerical factor is based upon ex- 

 periment. 



4. The paper then discusses briefly the 

 physical actions involved in the absorption 

 of sound by the walls and objects in a 

 room. 



On the Velocity of Light as affected by 

 Motion through the Ether: Edward W. 

 MoeIjET, Western Reserve University, 

 and Dayton C. Miller, Case School of 

 Applied Science. 



The theory of the Michelson-Morley ex- 

 periment contained in their paper of 1887 



was elaborated as far as seemed needful 

 in view of the negative result of their ex- 

 periment. This paper gives some account 

 of a more detailed theory and announces 

 some preliminary results of the more re- 

 cent experiments. 



Some Measures of the Speed of Photo- 

 graphic Shutters: Edward W. Morley, 

 Western Reserve University, and Day- 

 ton C. Miller, Case School of Applied 

 Science. 



A stroboscopic electrically driven tuning- 

 fork and a special camera containing a 

 cylindrical sensitive film were arranged 

 to obtain graphic representations of the 

 behavior of shutters. The exact manner 

 and time of opening and closing, as well 

 as the aperture and duration of exposure, 

 are recorded. 



Of the better grade of shutters designed 

 to give definite and adjustable exposures, 

 it was found that they were fairly con- 

 stant in operation, but that the actual 

 duration of exposure is often not even ap- 

 proximately that indicated by the maker. 

 Different shutters of the same make and 

 form give widely different exposures when 

 set for the same time. It was found in 

 all the shutters tested that the times 

 marked one seventy-fifth of a second or 

 less were all of the same duration, and 

 that this was much less than the shortest 

 marked time, namely, from three to four 

 thousandths of a second. If the time scale 

 for each separate shutter of this grade 

 were constructed upon tests of the shutter, 

 it might then be used to give practically 

 correct exposures. 



With the best shutters of the diaphragm 

 class the duration of exposure is nearly 

 independent of the aperture of the open- 

 ing. 



Some shutters of the cheaper grades 

 designed to give long, medium and short 

 exposures were found to give equal ex- 



