THE METEOROLOGY OF EDINBURGH. 75 



rate, thunderstorm rains usually fall short of an inch. August stands out prominently 

 for its rainstorms with thirty-three falls exceeding an inch. The period known as the 

 Lammas Floods shows to what an extent these heavy downpours have obtruded them- 

 selves upon public notice, and that long before the days of rain-gauges. July comes 

 second to August with twenty-one cases, while February and April have only six each 

 and March but five. It is of interest to note that two of the six heavy rains in Febru- 

 ary occurred within a week. The seasonal distribution was spring, twenty-seven cases ; 

 summer, sixty-six ; autumn, fifty-three ; and winter, twenty. From an examination of the 

 daily weather reports it was seen that the majority of notable downpours took place 

 during the passage of small shallow depressions moving slowly eastwards. Sometimes 

 the depression remained almost stationary for days. Enormous quantities of rain 

 were then precipitated, 7 inches, for example, falling in five days during August 1877. 

 In a few cases, principally in winter, the rain was general over the country, but as a 

 rule the western parts of the country were not affected by the cyclonic storms which 

 gave the heavy rains on the east coast. The general direction of the wind during the 

 rainstorm was noted, the percentage frequency being as follows, viz. : — 



N. 



N.E. 



E. 



S.E. 



S. 



s.w. 



w. 



N.W. 



5 



15 



32 



9 



3 



9 



21 



6 



The maximum number of cases took place with winds from the east, a well marked 

 secondary maximum being observed with winds from the west. If we weigh the observa- 

 tions so as to allow for the relative frequency of the winds during the ninety-two years, 

 we obtain quite a different windrose, as it is called. The overwhelming preponderance 

 of sea-winds during the occurrence of heavy rains now becomes apparent, while the 

 secondary maximum with west winds — a maximum due to the frequency with which 

 these winds blow — vanishes. Thus, approximately, in 1,000 days of wind there will be ten 

 rains exceeding an inch with a north-east wind, and nine with an east wind, while only 

 two cases may be expected with a south wind. The values for the other winds are N. 6, 

 S.E. 6, S.W. 3, W. 3, N.W. 4. The comparative infrequency of heavy rains with south- 

 east winds is doubtless due to the fact that they have been deprived of much of their 

 moisture by the Lammermoors over which they had previously passed. In Aberdeen- 

 shire, as shown by Dr Buchan, the south winds blow against the cold slopes of the 

 Grampians with the result that there they are by far the wettest. Mr Symons has 

 stated that there is no part of the British Isles, however dry, where 4 inches of rain may 

 not fall in twenty-four hours. The Edinburgh record bears this statement out, for 

 although there are only three rains exceeding 3 inches in the ninety-two years, yet one 

 was above 4 inches, no less a quantity than 4*20 inches having fallen on December 9th, 

 1787. On that occasion there was a great flood in Leith Harbour, greater than ever 

 remembered. The flood was as high at low water as at ordinary full tide. Much 

 damage was done to the shipping, while several casualties involving loss of life were 

 reported from Leith and other parts of the country. It cannot be too strongly urged 



