544 



TRANSACTIONS OP SECTION A. 



in the free atmosphere. Three causes of very regular waves were shown, two 

 occurring during or instantly after a rapid increase of pressure, the third during 

 a more constant, but somewhat irregular, rise. The variogram of a more com- 

 plicated line-squall consisted also of rather regular waves. 



In all those cases in which one had pronounced regular oscillations, some 

 hours after their occurrence a line-squall was observed ; and, vice versa, in most 

 cases of stronger squalls regular waves of pressure were developed some time 

 before. Such oscillations may therefore be due to some disturbance on the front 

 of secondary or V-shaped depressions, in whose rear cold air is flowing in. 

 This suggestion is confirmed also by cloud observations. 



The study of the minor fluctuations of the atmosphere, and especially of 

 regular waves, may therefore be not only of purely theoretical interest, but also 

 useful in forecasts as an indication of changes in the free atmosphere. 



2. Observations on the Upper Atmosphere during the Passage of the Earth 

 through the Tail of Halleifs Comet. By W. H. Dines, F.R.S. 



This paper gave the results obtained from thirteen ascents of registering 

 balloons from Ditcham Park, Pyrton Hill, and Manchester. The records do not 

 show any result that can reasonably be put down to the action of the comet, but 

 they nearly all agree in showing that at that particular time rapid variations of 

 temperature were in progress in the upper air. It was pointed out that an un- 

 usual number of oscillations were recorded on the microbarograph during that 

 week, and the possibility of the two phenomena being connected was discussed, 

 and the difficulty of finding any reasonable explanation of the large changes of 

 temperature that are known to occur in the upper atmosphere was pointed out. 



3. Radiation Pressure in Cosmical Problems. 

 By J. W. Nicholson, M.A., D.Sc. 



The paper dealt mainly with a determination of the pressure produced 

 by a train of plane electromagnetic waves incident on a totally reflecting sphere. 

 This problem has been worked out previously by Schwarzschild, 1 but more 

 extended calculations do not support his numerical results in detail. Yet the 

 general character of the results is preserved. When the incident light is mono- 

 chromatic, the following table may be constructed, where p is the pressure, a 

 the radius of the sphere, and A the wave-length : — 



1 Sitz. der Math. Phys. zu Munchen, 1901-02, p. 293. 



