H4 Presidential Address 



posed to consist of rigid granules in contact, and where 

 "matter " was the hollows or cavities or regions of greater 

 interstitial capacity existing among them. These regions 

 could readily travel about from one part of the granular 

 structure to another; and this represented the motion of 

 matter in the scheme. Such an ether is very unlike any 

 contemplated by the author. 



Page 22 



In the Physical Review for August, 1913, Professor R. 

 A. Millikan summarises the results of most recent and 

 trustworthy determinations of molecular magnitudes, and 

 among them of Avogadro's constant. It may be conven- 

 ient to quote some of them here: 



Unit of electric charge, e =4.774X10 I0 electrosta- 

 tic units. 



Number of molecules 



per gramme molecule, N =6.062 Xio a *. 

 Molecules per cubic 

 centimetre of gas at o 

 and 76, n =2.705 Xio 1 '. 



Planck's constant h =6.62 Xio 2 ?cgs. 



The number of H 2 O molecules in a cubic centimetre, or 

 say 15 grains, of water is therefore -33Xio 23 ; and the 

 number of atoms io 2 3. 



Now io 2 3 cubic centimetres of water weigh lo 1 ? tons, 

 = io 8 cubic kilometres, 

 =25 million cubic miles, 



which would form an ocean 6000 miles long, 2000 miles 

 wide, and 2 miles deep, corresponding therefore very 

 fairly to the North Atlantic Ocean. 



Page 23 



For a further discussion of incommensurable quantities, 

 and of the impossibility of expressing the majority of 



