74 



MR ROBERT COCKBURN MOSSMAN ON 



instance to the former class, viz., absolute droughts. The total number of these during 

 the ninety-two years under review was 65. Their distribution throughout the year (as 

 will be seen on looking at Table) is somewhat irregular, June having the greatest number 

 with 10, closely followed by February and March with 9 each. The minimum is 

 reached in Autumn, November having only 2, and October 3. The secondary minimum 

 in April and May is of interest as is the sharp drop after July. We may state that the 

 droughts have been entered to those months in which they commenced. 





Jan. 



Feb. 



Mar. 



Apr. 



May. 



June. 



July. 



Aug.' 



Sept. 



5 

 19 



Oct. 



.3 

 17 



Nov. 



Dec. 



Year. 



Number of Droughts, 

 Mean duration, days, 



3 

 20 



9 

 18 



9 

 20 



5 



19 



4 

 21 



10 

 18 



7 

 19 



3 



18 



2 

 16 



5 

 18 



65 

 18'6 



As regards individual years, the greatest number of droughts observed was three in 

 1786, 1825, 1829 and 1867, while none occurred from February 1787 to July 1795, a 

 period of eight years and three months. A recent instance of a long spell without one was 

 from August 1876 to May 1884, or seven years and nine months. The longest period 

 without rain occurred in 1786, when none fell for thirty-three days, viz., between May 24 

 and June 25. The water supply in Edinburgh fell short during this year, the community 

 being put to much inconvenience thereby. Other long spells without rain were from 

 March 13 to April 11, 1825, and from June 24 to July 22, 1869, periods of thirty and 

 twenty-nine days respectively. Of the sixty-five droughts recorded, sixteen exceeded 

 twenty days while four lasted a month. Nearly all the dry periods occurred in early spring. 

 Only on one occasion during the three months October to December did a drought last for 

 a longer time than seventeen days. As to the atmospheric causes concurring in such long 

 dry periods, little can be said. We know that droughts are due to the unwonted 

 prevalence and persistence of anti-cyclonic systems over Western Europe, but to say 

 more than this would be to enter on the ground of pure speculation. 



With regard to heavy rains, all falls of an inch or more in the twenty-four hours 

 were extracted for the ninety-two years under consideration (see Table XXX I.). An 

 inch a day in this part of the country is looked on as a heavy rainfall, being equivalent 

 to 101 tons or 22,623 gallons of water per acre. The total number of cases as will be 

 seen from the following Table was 165, giving an average of very nearly two per 



Month. Jan. Feb. Mar. 



Falls of TOO inch or more, 7 6 5 



Apr. May. June. July. Aug. Sept. Oct. Nov. Dec. Year. 

 6 15 12 21 33 20 18 15 7 165 



annum. The heavy falls were distributed among the years in a most capricious manner. 

 For instance, there were eight such rains in the year 1808, while 1809 and 1877 had 

 seven each. On the other hand not a single case was observed from September 1884 to 

 August 1889. The number of heavy falls during thunderstorms was one in May, two in 

 June, ten in July, and four in August. It would thus appear that in Edinburgh, at any 



