﻿GG8 Dr. Norman Campbell on the 



The density, velocity, and temperature maybe approximately 

 evaluated b} r the use of spheroidal coordinates, but the 

 process is rather laborious and I shall merely state the 

 nature of the result. This depends on the position of the 

 point under examination with regard to a certain surface 

 defined by the equation 



r 4 + r ? = ^-5— r cosec- A. 

 or 



This surface is somewhat similar to the surface of minimum 

 pressure and lies a little inside it. If r =2a, which is 

 roughly the value it should have, then the surface cuts the 

 equator at 5*1 a. The approximation goes as follows : — For 

 points well inside the surface the correction is very small. 

 Taking an atmosphere of hydrogen at 30° abs. it is about 

 1 mm. per sec. at r = ±a at the equator. On approaching 

 the surface the lag increases rapidly, while the density 

 diminishes little apart from the ordinary diminution due to 

 height. Outside the surface the density falls off very quickly 

 and the lag changes slowly. In this region there is certainly 

 a large disturbing factor in the presence of molecules describ- 

 ing hyperbolic paths and also in reality there must be many 

 molecules describing permanent elliptic orbits. 



It is therefore possible to say that no lagging effect will 

 appear up to somewhat more than four radii from the earth's 

 centre. Any discussion of phenomena at a greater height 

 would have to take the hyperbolic paths into account and 

 the presence of permanent orbits and probably also the 

 arrival of molecules from outer space. These last two 

 factors are entirely unknown and the density is very small, 

 so that a fuller investigation does not seem advisable. 



My thanks are due to Dr. Schuster for suggesting to me 

 this problem, and for the interest he has taken in it. 



The University, 

 Manchester. 



LXL Note on the Electrical Resistance of Xylol- Alcohol 

 Mixtures. By Norman Campbell, Sc.D* 



IN the Philosophical Magazine for August 1911, pp. 301, 

 302, I described certain liquid resistances which may be 

 used for the same purposes as the resistances of ionized air 

 generally associated with the name of Bronson. Some further 

 investigation has been made into such properties of the liquids 

 as are important for these purposes. 



* Communicated bv the Author. 



