THE METEOROLOGY OF EDINBURGH. 699 



sudden abatement of thunderstorms during this interruption of temperature is of 

 interest. 



July. 



During the month there are two periods characterised by low and high pressure, 

 each of which is associated with well-marked climatological features. The month 

 opens with pressure above the mean, but falls to a minimum on the 7th, about 

 which time thunderstorms rise to their annual maximum with torrential rains. 

 During the first week there is a decided decrease in winds from the N., N.E., 

 and E., while a corresponding increase is observable in winds from the W. The 

 first high-pressure area embraces the ten days ending with the 18th, in the middle of 

 which period temperature rises to the annual maximum on the 15th. Low pressure 

 prevails from the 18th to the 26th, during which period E. winds increase, a point to 

 be noted in connection with the excessive rainfall at the time. Temperature during 

 the passage of the low pressure area continues to fall slowly. The month closes with 

 high pressure, although with rainfall well above the annual mean. 



August. 



Throughout the month pressure is on the whole low and steady. The most pro- 

 minent low-pressure period extends over the first half of the month, towards the close 

 of which an enormous increase of rainfall takes place, known in Scotland as the Lammas 

 floods. The absolutely wettest day of the year on smoothing the curve is August 13, 

 the precipitation being then 96 per cent, above the annual mean. About this time 

 a curious increase in the frequency of S.W. winds takes place, the W. wind for the 

 time blowing with diminished frequency. A secondary maximum of temperature 

 culminates on the 13th of the month, the temperature of the sea reaching its annual 

 maximum at this time. After the middle of the month pressure rises slowly, the 

 torrential rains abate, in connection with which the rapid decline of thunderstorms is 

 of interest, electrical disturbances being of comparatively rare occurrence during the 

 second half of the month. At the close of the month W. winds blow with greater 

 persistence than at any other period of the year. 



September. 



During the greater part of September the tendency is for the anti-cyclonic type 

 of pressure, which is most pronounced from the 11th to the 20th. Calms are now 

 at their annual maximum. Rainfall is still above the mean, but shows a distinct fall 

 from the previous month. The maximum temperature shows a rapid fall after the 

 13th, which does not appear in the minimum temperatures until the 16th; the fall 

 ceases in both cases on the 22nd, after which a slight rise occurs, due apparently to the 

 greater frequency of westerly winds at the time. During the rapid fall of temperature 



