Proceedinys. 37 



obtained by telegraphic reports of the height of the barometer 

 from the various stations scattered over the kingdom and the 

 coasts of France, Norway, &c., as shown on the map, at eight 

 o'clock in the morning and six o'clock in the evening ; some 

 also report at two o'clock in the afternoon. The isobar is 

 drawn in curves from one station to another where pressure 

 is reported to be alike, and knowledge of the position of these 

 isobaric lines lies at the very foundation of all that we know 

 about the weather. 



The track of cyclones is, in the large majority of cases, 

 from S.W. to N.E., and happily the greater number pass to the 

 W. and N. of our islands, often missing England ; they affect 

 the W. coast of Ireland, giving a real grievance to that un- 

 happy country, and the N. of Scotland. In their front they 

 are accompanied by high temperature and much moisture in 

 the air, the sky becomes overcast, and there is a setting-in 

 of mist and rain. As they pass away the rain ceases, the 

 temperature rapidly falls, and the sky generally clears. At 

 their approach from the S.W. the wind becomes S.E. ; as 

 they pass to the W. the wind veers to S., and when they have 

 travelled to the N. the wind becomes W. ; finally they pass 

 away from our neighbourhood beyond Norway, and the wind 

 is then N. and N.E. All the time you will see that, keeping 

 the centre on our left, our back is to the wind, as it has 

 gradually veered round with the progress of the storm. 



Wind is said to " veer" when it changes with the sun, and 

 to " back" when it changes against the sun ; in this country 

 it more often veers than backs, because the storms nearly all 

 pass to the north of our island ; and the wind veers when the 

 depression passes to the north of us, and backs when it passes 

 to the south. 



All that we have said about the wind so far has been to 

 explain its direction. We must now consider what is the 

 cause of its varying force. After the explanations that have 

 been given, this is comparatively simple. The hollows and 

 ridges of the atmosphere, and the attempt made by it to re- 

 gain a level, generate the motion or wind ; and the deeper 

 the hollows and the steeper their sides, the greater is the 



