MEAN SCOTTISH METEOROLOGY. 271 



of the single months, which has for its mean = 3'25, — has for its Max. in December 

 = 4*07, and for its min. in April = 2*24 inches, British. 



Table X. seeks to record the mean amount of strength of wind in each month of each 

 year; the mean of the whole being 1*73 lbs. constant pressure by night and by day on 

 every square foot of surface; implying a velocity of over 18 miles an hour. A high return, 

 showing perhaps the effect of proximity to the sea-board of most of the Scottish stations, 

 however centrally in the country the mean of the whole may be located. Or perhaps it 

 may indicate the difficulty of observing the true mean pressure of the air through the 

 whole 24 hours, both independently of the impact of the rain drops, and the effect of 

 momentary gusts on the feelings of humanity at the instant of observation. The annual 

 cycle however comes out pretty evidently, with a Max. in February = 2*11, and a min. 

 between July and August = 1'34 lbs. on the square foot. 



Table XL gives the mean monthly number of days on which winds of Northerly direc- 

 tion blew, that is, all those entered North, and half of those entered N.-east ; with the 

 same for those entered N.-west ; and amounting per mean month to 5. The annual 

 cycle of these North winds is rather obscure, having something like two Max., one in 

 April and one between November and December, each = 6 ; and two mm., one in January 

 and February = 4, and another in August = 5. 



Table XII. gives similarly the number of days per month, on which Easterly winds 

 blew, viz., 6. The annual cycle showing a Max. between April and May = 8, and a min. 

 in December = 4. 



Table XIII. the number of days per month, on which Southerly winds blew, viz., 8. 

 The annual cycle having a faint Max. = 9 in January, and a faint and short-lived min. 

 in March = 6. 



Table XIV. the number of days per month on which Westerly winds blew, viz., 10. 

 The annual cycle having its Max. in August = 12, and the min. in April = 8. 



Table XV. gives the mean number of hours of Sunshine in each month, amounting on 

 a mean of all the months to 136; but varying between December and June from 60 to 

 217, for astronomical as well as meteorological reasons. 



Table XVI. gives the estimated mean amount of Cloud per month, in decimals and 

 tenths thereof, of the hemisphere; being, for a mean month = 6 "4. But varying between 

 January and May between 67 and 6*2; or indicating a never very astronomical observ- 

 ing climate. 



Tables XVII. and XVIII. both refer to Lightning. The former gives the mean 

 number of days it is seen per average month, = 1 *6 ; and the latter records the number 

 of stations reporting it = 1 5. 



The former kind of return arrives at its maximum in July, and = 2*5 ; while the 

 latter kind reaches its maximum also in July, and = 29. 



Again the former kind attains its minimum in February, and=l"l ; while the latter 

 has its minimum very near it, or in March, and then registers 6. 



So that multiplying the two kinds of return together, we have — 



