542 



MESSRS OMOND AND RANKIN ON THE 





Jan. 



Feb. 



March. 



April. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



East, 

 West, . 



11 

 39 



16 



24 



8 

 18 



7 

 87 



4 

 30 



47 

 51 



36 



19 



13 



10 



5 

 9 



18 

 19 



29 

 26 



U 

 48 



June was an exceptionally dry month all over Scotland in several of the years, 

 and it is probable that in a longer series of years the extremely low values of this 

 table — only about half the mean fall — would be modified. Comparing the other 

 months w r ith the wind Tables IV. and V., we see that the heaviest rainfall on the 

 west coast occurs during the winter maximum of westerly winds, and the least during 

 the spring maximum of easterly winds, and that the summer secondary maximum of 

 westerly and southerly winds in July and August does not affect the west coast, but 

 does largely increase the east coast rainfall, July being actually the month of heaviest 

 fall there. If we combine the east and west percentages, and assume the result to 

 be representative of the rainfall for the whole country, we get the greatest excess in 

 November. The winds of November have this peculiarity, S.W. is in excess both 

 on Ben Nevis and at sea-level, but E. and N. are slightly below their mean 

 at sea-level, and are above it on Ben Nevis, pointing to the fact that the cyclones 

 which have caused the heavy rainfall of November have not extended upwards to 

 the height of Ben Nevis, but have there caused reversed or outflowing winds. In 

 connection with this, it may be noted that while the November rainfall of the east 

 and west coast stations average 27\ per cent, above their means, that of Ben Nevis 

 is only 26 per cent, above its mean ; a difference too small to lay any stress on, but 

 at least not contradictory of what is indicated by the winds, viz., that Ben Nevis is 

 frequently at that season above the inflowing and ascending air of the cyclones from 

 which the greater part of the rainfall comes. The month with the greatest difference 

 between the east and west coast rainfall is December, in which the former is 14 per 

 cent, below, and the latter 48 above, its mean. The winds of December show a marked 

 increase of S.W. and W. at sea-level, but of N.W. and N. on Ben Nevis, and a 

 diminution of N.E., E., and S.E. at sea-level, and of E. and S.E. on Ben Nevis, 

 indicating that the cyclonic storms of this month were of sufficient depth to include 

 Ben Nevis, and give winds there only differing slightly from those at sea-level. The 

 December rainfall of Ben Nevis for these six years is about 70 per cent, above the 

 monthly average. It would appear that the cyclonic winds of December, mostly 

 W. and S.W., are largely drained of their moisture in passing over the hills of western 

 Scotland, although the region of precipitation in them extends to a height so far 

 exceeding the highest of these mountains as to enormously increase the rainfall there. 



From what has been stated above, it will be evident that no hill station, yet in 

 operation, can be regarded as being in the true upper currents of the atmosphere, 

 and that we are still dependent for our knowledge of their motions on observations 



