﻿252 Messrs. Trivelli and Righter on Silbersteins 



distance of the centre of buoyancy B (the centroid of 

 the displaced liquid) from the metacentre M is given by 

 BM = AK 2 /V, where V is the volume of the displaced liquid 

 and AK 2 is the moment of inertia of the water-line area 

 about the intersection of the wedges of emersion and im- 

 mersion. The equilibrium of the floating body is stable if 



Fig. 8. Fig. 9. 



M is above G, the centroid of the floating body, that is 

 if BM > BG ; it is unstable if BM < BG ; and it is neutral if 

 BM = BG, that is when M coincides with G. In figure 5 we 

 may suppose the complete cylinder floating in water so that 

 abed is the water-line area. The cylinder is obviously in 

 neutral equilibrium so far as turning about the axis 00' is 

 concerned. Thus M lies in the line 00', and we have 



0G=^ 



University of Glasgow, 

 May 1,1922. 



XVIII. Preliminary Investigations on Silbersteins Quantum 

 Theory of Photographic Exposure. By A. P. H. Teivelli 

 and L. Righter*. 



Introductory. 



THIS paper is the first of a number of investigations 

 now being conducted in this laboratory to test experi- 

 mentally the light-quantum theory of photographic exposure 

 recently proposed by Dr. Silberstein before the Toronto 

 meeting of the American Physical Society. 



* Communication No. 141 from the Research Laboratory of the 

 Eastman Kodak Company. 



