THE BAROMETER AND THE WEATHER. 157 



chart. This interesting and important generalization is 

 called "Buys Ballot's Law." In spite of the proverbial 

 fickleness of the winds this simple law is -rarely infringed, 

 though it may require a slight modification of statement 

 inasmuch as the wind does not move in circles round the 

 vacuous space, but in spirals, and thus it blows not quite 

 square to the back, but rather obliquely, or a little on the 

 right side. This is shown by the arrows in the charts, and 

 is most strikingly displayed in the chart for October 6th, 

 between the isobars of 30.3 and 30.5. To take, in Ireland, 

 the position required by Buys Ballot's Law, one must have 

 stood facing the east, and accordingly, the westerly wind 

 would then blow upon one's back. In Paris, at the same 

 moment, the position would be facing south-east, and the 

 w.ind was curving round accordingly. Further south at 

 Bordeaux or the Pyrenees the position becomes almost 

 reversed, i.e., facing south-west, and the wind is reversed 

 in equal degree. 



Here, then, on these days we had the chief conditions of 

 wind and rain, a steep and increasing barometric gradient, 

 and a flow over our islands of humid air from the south 

 and west regions of the great Atlantic. Strong winds and 

 heavy rains did follow accordingly; and the prophetic 

 warnings of the Meteorological Office, which are conveyed 

 by means of signals displayed on prominent parts of the 

 coast, were fulfilled. 



Mr. Scott, the Director of the Meteorological Office, 

 tells us that "The degree of success that has attended our 

 warnings in these islands, on the average of the last two 

 years, has been that over 45 per cent have been followed by 

 severe gales; and over 33 per cent in addition have been 

 followed by wind too strong for fishing-boats and yachts, 

 though in themselves not severe gales; this gives a total 

 percentage of success of nearly 80." 



In winter the movements of the air are more decided, 

 and the changes are often so rapid that the warning some- 

 times comes too late. With increased means i.e., more 

 money to cover additional work, and more stations better 

 results might be obtained. The United States expend 

 50,000?. a year in weather telegraphy, exclusive of salaries, 



