168 Proceedings. 



move, than in the opposite direction. This empirical law 

 we now know has some justification in Germany, from' 

 which country Dove chiefly derived his observational data ; 

 but we also know now, that this is due to the fact, that the 

 cyclones which affect Germany pass chiefly due north of it, 

 in a direction from west to east. Nevertheless, at the time, 

 Dove's law of the rotation of winds seems to have been 

 accepted by meteorologists as a law of nature. To doubt it 

 was heresy. 



" Buys Ballot, from a careful consideration of the direction 

 of the wind, observed not in the same spot at different 

 times, but at different spots at the same time, established 

 the laws which have since received ample confirmation. If 

 at any place on the earth there is a barometric depression, 

 the air will circulate round that depression in a direction 

 opposite to that in which the hands of a watch move. 

 There will also be an inward motion, due to friction against 

 the ground, so that each particle of air will describe a 

 spiral towards the barometric minimum. In the centre of 

 the cyclone there will be an ascending current of air, main- 

 tained by the condensation of moisture. 



" The principal facts established by Buys Ballot had 

 been already deduced, chiefly from theoretical considera- 

 tions, by an American investigator, Ferrel ; but his work 

 remained unknown. Although priority belongs to Ferrel, 

 Buys Ballot had to undertake the difficult task of con- 

 tending against Dove's authority, and convincing the 

 scientific world. The ability and skill which finally ensured 

 his success, are testified to by the unanimous regard and 

 esteem with which in his later years he was looked upon by 

 all his scientific contemporaries. 



"The present form of the weather charts with the draw- 

 ing of the lines of equal pressure, or isobars, which are now 

 published by the Meteorological office, and which have helped 

 so much to advance our knowledge of atmospheric circula- 



