338 Mr. Carl Barus on the 



)void. 



Factor. 



King. 



m. 



N. 



a. 



20 



•0848 



2-41 



30 



•0432 



1-22 



40 



•0266 



•76 



50 



•0181 



•52 



00 



•0054 



•15 



CO 











Now Lord Rayleigh has given a graphic construction for 

 ovoids, which Ewing expresses in the following words : — 

 From the ordinary curve of magnetization for infinitely long 

 ovoids, that corresponding to a given finite one may be 

 obtained by shearing the diagram parallel to the axis of 

 abscissa? through an angle, which is simply determined by N, 

 therefore also by the given ratio of axes. By the above the 

 curve for closed rings may now, in the same way, be sheared 

 into a diagram for a ring with a given angular gap. 



The analogy of this process with the Hopkinsons's well- 

 known graphic method is obvious, though at first essential 

 differences appear to exist ; e. g. the quantities used for co- 

 ordinates are not the same in both cases. However, a com- 

 parison in detail finally leads to the identification of both 

 constructions, so that in any given particular case the curves 

 would exactly overlap, supposing the coordinates to be 

 measured to proper scales. Our problem, a solution of which 

 was first necessitated and afterwards approximately given by 

 machine practice, has therefore now been solved to the same 

 order of approximation by physical methods. 



The degree of this approximation, the allowable limits for 

 thickness of ring and width of air-gap, the amount of 

 " leaking " of lines of force, &c, can only be determined by 

 experiment on as large a scale as possible. 



XXXIX. The Isometrics of Liquid Matter. 

 By Carl Barus*. 

 [Plates IX., X., XL] 



IT was my original intention to communicate the second 

 part of this paper only ; but I found that the data there 

 given would not be intelligible without a clear account of the 

 method of the work. Accordingly I supplied the first part 

 from the ' Proceedings ' of the American Academy (June 1890), 

 where a fuller account of my compressor may be found. 



* Communicated, with the permission of the Director of the U.S. 

 Geological Survey, by the Author. 



