INFLUENCE OF HIGH WINDS ON BAROMETER AT BEN NEVIS. 



495 



the cause of the retarded velocity of the wind where it is noted is the impact of the air 

 on the face of the tremendous cliff, close to the top of which the Observatory is built, 

 by which the stream lines are deflected upwards. Now, in these cases the depression 

 of the barometer is very much greater than what occurs with equally strong winds 

 from other directions, and clearly indicates the formation of a restricted space of low 

 pressure outside and around the buildings of the Observatory. Another curious result 

 •observed with winds from S.E. to S.W. is that the barometer at the top, reduced to sea- 

 level, exceeds the reduced low-level barometer at Fort- William, when the wind velocity 

 is about 6 miles an hour. May not this increased pressure, accompanying wind 

 ascending the slope of the hill, give the explanation of the thin clear space frequently 

 seen on the very ridge of a hill otherwise cloud-topped, and also of the very different 

 force of wind on the two sides of a ridge lying approximately at right angles to the 

 .direction of the wind ? 



