Irregularities of Meteorological and Magnetic Phenomena. 57 



The light from the negative point is less than that from the 

 positive. Brass points were used when making this com- 

 parison, but no difference was observed with other points. 

 The potential-difference was about 30,000 volts. 



Comparison of the Actinic Poiver of the Brush with that 

 of Light. 



In order to roughly test this an ordinary negative was 

 taken and fixed in a frame together with a piece of bromide- 

 paper. The frame was then exposed in the dark room to the 

 light from a standard wax-candle. The same negative was 

 then treated in the same way and exposed to the brush-dis- 

 charge for a given time. The prints were then fixed and 

 compared in order to see if they were over or under exposed. 

 The experiments were then repeated until the effects were 

 equal. After many experiments the nearest comparison that 

 could be obtained was that the light from the candle at a 

 distance of 15 centim. and 20 seconds' exposure produced 

 the same effect as that from the positive brush at the same 

 distance and 15 minutes' exposure. From this the relative 

 powers would be as 1 to 45. The potential-difference when 

 making these tests was about 30,000 volts. 



On comparing this number with that obtained from the 

 photometric experiments it will be. seen how widely they differ, 

 and it may therefore be considered as certain that the emana- 

 tion from the point consists very largely of those waves 

 which are capable of bringing about chemical changes. 



IV. On the Analogy of some Irregularities in the Yearly 

 Range of Meteorological and Magnetic Phenomena. By 

 Dr. VAN RlJCKEVORSEL *. 



[Plate II.] 



AT the Toronto Meeting of the British Association f I 

 called the attention of Section A to the fact that if the 

 normal temperatures for every day of the year are plotted 

 down in a curve, such curves are strikingly similar for 

 stations spread over a very large area. An area which is 

 larger than our continent for some of the particulars shown 

 by these curves, while for others it extends over Western 

 Europe only, or over part of it. 



I am now able, to a certain degree, to give an answer to 

 the query at the end of that paper : " Is it temperature alone 

 of which the irregularities are so extremely regular ? How 



* Communicated by the Author. 



t Paper published in the Phil. Mag. for May 1898. 



