38 



Mr. J. A. Broun on Simultaneous 



[May 11, 



While for the moyement March 31 to April 3 they are : — 



in. 



Simla 0-066 



Madras 0-0G9 



Singapore 0-083 



St. Helena 0-070 



The first movement seems to diminish on proceeding southwards from 

 Madras ; the second remains nearly constant from Madras to St. Helena, 

 and is least at the most northerly station. 



Perhaps the most remarkable fact brought out in this discussion is 

 the fewTiess of the cases in which a change of pressure perceived at 

 one station is not felt at the others ; and this holds true for changes of 

 not more than one hundredth of an inch of mercury. It will also be 

 remarked that though Simla is 7100 feet above the sea, the movements 

 are not diminished by this diminution of the superambient air ; what 

 part the higher latitude may have in this result cannot at present be 

 told. 



Eemembering the distances of the stations, it will be seen that no 

 theory of propagation of waves by convection-currents or by rarefactions 

 and condensations due to them, founded on the facts as yet known to 

 us, can explain these maxima and minima which occur nearly simul 

 taneously on the level of the sea at Singapore and Madras, at St. 

 Helena 1800 feet and at Simla 7100 feet above the sea-level, under 

 conditions of temperature, humidity, clouds, wiuds, and weather dis- 

 similar in every respect *. The resemblance of the variations considered 

 to those of the earth's magnetic force suggests the idea that they may 

 be due to different modes of action of the same cause, 



I have no doubt that by more extended investigations we shall arrive 

 at the explanation of many meteorological phenomena by the action of 

 this cause, which has not hitherto been taken into account. I shall con- 

 clude this note with the w^ords of De Luc in the dedication of his work 

 on the atmosphere to the members of the French Academy of Sciences : — 

 "J'aicru m'apercevoir, en etudiant la physique, que, depuis que cette 

 science fe'est assez et^ndue pour quon ait forme des systemes sur presque 

 tons les objets qu'elle embrasse, deux prejuges contraii'es nuisoient egale- 

 ment aux progres de la verite ; trop de defiance contre les solutions jugees 

 impossibles, et trop de confiance dans celles qui sont adoptees "t. 



Received May 24, 1876. 



Additional remarl\ — On reading the preceding note to the Eoyal 

 Society, I pointed out that one of the most marked exceptions to the 



* E. g., it snowed all daj- on the 24th January at Simla, while at Madras and 

 Singapore the daily mean temperatures were those of the month at each place, or 70° 

 and 79° respectively. 



t Eecherches sur les modifications de I'atmosphere. Par J. A. de Luc. Nouyelle 

 edition. Par.s. 1784, 



