﻿62 Prof. G. N. Antonoff <m the 



In each case considered we have only to replace O by an 

 increased value fl' to obtain a motion for which the system 

 of isobars travels eastward at a uniform speed (CI' >Q). 



Each of: the above solutions has been given to apply to an 

 isothermal atmosphere, and in every case considered the 

 fluid moves so that no element of fluid undergoes change of 



density. That is, ~ — h s: — H ^— =0 at each point. Provided 

 "* 3# dy d* r 



this condition is fulfilled, any solution obtained for motion of 

 an atmosphere, all at one temperature, can readily be trans- 

 formed to suit an atmosphere in convective equilibrium 

 (p = Jepy), or one in which pressure is any given function of 

 density. Thus, taking the motion represented by (41) above 

 in an atmosphere in convective equilibrium, we have merely 



to replace log/o and log/o in (43) by — —. ,P y ~ l and - po 7 " 1 



respectively, all other conditions being unchanged. 



VI. The Breaking Stress of Crystals of Rock- Salt. 

 By Prof. G. N. Antonoff, Z>.Sc.(Manch.) *. 



IN a paper published in Phil. Mag. vol. xxxvi. Nov. 1918, 

 I have developed a theory of surface tension under the 

 assumption that the attraction of molecules is due to electrical 

 or magnetic forces, or both. Instead of assuming a uniform 

 field round the molecules as it is generally accepted acccording 

 to Laplace, I accepted the view that the molecules act as 

 electrical doublets, and from the theory of potential I 

 deduced that the attraction between them must be inversely 

 proportional to the 4th power of the distance, provided the 

 distance between the doublels is large compared with their 

 respective lengths. 



It was shown that the attraction between the doublets can 

 be represented by an expression of the type 



kP 



where k is a constant, I the length of the doublet, and d the 

 distance between them. In these calculations the magnetic 

 forces were disregarded altogether, as the law of attraction 

 between small magnets would be just the same, so that they 

 could only have an effect on the value of k. 



* Communicated hy Dr. J. W. Nicholson, F.R.S. 



