PROCEEDINGS 



OF 



THE ROYAL IRISH A (J A DEMY 



PAPERS READ BEFORE THE ACADEMY 



I. 



PECULIARITIES IN BAROGHAPH CURVES 

 CHARACTERISTIC OF APPROACHIIS^G STORMS. 



Ry AVILLIAM EDWARD WILSON, F.R.S. 



Read February 8. Ordered for Publication February 10. 

 Published February 24, 1904. 



In 1889, I obtiiincd one of the recording aneroids by Richard of Paris. 

 It is the large scale instrument, and draws barograms of twicer the 

 amplitude of the ordinary mercurial barometer. With the object of 

 studying the curves obtained with tliis instrument, I had a long 

 board attached to the wall of my laboratory, on which I could pin up 

 the weekly records in a long line of some months' duration. It was 

 not long before I found that, at uncertain intervals, there was reproduced 

 over and over again a certain type of curve. The period of completion of 

 one set was not always the same, but varied from about three weeks 

 to something less than a week. I can offer no solution of this extra- 

 ordinary curve ; but that it is not due to mere chance is, I think, 

 evident from the frequency with which they are reproduced. Tlie 

 late Prof. Fitzgerald took a great deal of interest in them ; and although 

 he could not solve them, he said he was quite certain that they had a 

 physical meaning. The fundamental property of these curves is this. 

 After a rather low pressure, the barometer rises fairly steadily until 

 generally above the normal. After an uncertain interval, n fall i^ets 



H. I. A. PROC, VOL. XXV., SEC. A.J A 



