16 



Proceedings of the 



If we take a middle line, which includes the mountain range that traverses 

 England from south to north, and extends through the centre and west of 

 Scotland, we find that here is the greatest amount of deposition. In the 

 mountains of Cumberland and Westmoreland, from 50 to 140 inches of 

 rain fall annually. South of this range throughout England, from 36 to 

 46 inches are deposited. In Scotland, from the Lowther Hills to the 

 mouth of the Clyde, from 47 to 50 inches. A third line embraces the west 

 coast near the level of the seci. At Land's End, the annual fall is 42 inches, 

 in Exmoor, 5Q inches. As we proceed farther north, the mean fall de- 

 creases to 38 and 35 inches. Taking the western half of Britain, includ- 

 ing the mountain regions, the annual mean of the rain stations is 45*5 

 inches, but considering that there is a deficiency of data for the elevated 

 regions of Wales and the north-west of Scotland, and a preponderance of 

 coast stations where the fall of rain is moderate, we may suppose that the 

 actual fall for the western half of Britain is at least 5 or 10 inches more than 

 this average ; that is, from 50 to 55 inches. We thus see that the moun- 

 tain regions of Britain, by their superior elevations, compared with the 

 valleys and plains, and by the consequent diminution of their surface tem- 

 perature, become the condensers of the moisture of the warm and moist 

 southerly winds. From the interesting data of Mr Miller of the Lake 

 district of England, it is also demonstrated that the greatest amount of 

 deposition takes place at an elevation of 1900 feet, and above this, the 

 fall of rain rapidly diminishes. 



In Ireland the greatest amount of rain- fall occurs on the south-west 

 coast, 59 inches falling in the vicinity of its highest range of mountains. 

 In the low lying central plain of Ireland the annual fall is 23 and 24 inches, 

 while on the mountain ranges of the north-east and south-east from 30 to 

 37 inches fall. 



If we divide the year into three periods of four months each, beginning 

 the winter period with November, we shall find that most rain falls in the 

 summer and winter months, and least in spring. This is shown in the 

 following tabular view : — > 



Penzance, Cornwall, . . 



Keswick, 



Glasgow, 



Gilmourton, Lanarkshire, 

 Glencorse, Pentlands, 



London, 



Boston, 



York, 



Spring. 



Summer. 



Winter. 



Inches. 



Incites. 



Inches. 



12-2 



13-5 



17-4 



16-0 



24-0 



19-9 



8-3 



9-8 



15-5 



11-6 



173 



18-8 



102 



14-3 



11-6 



6-7 



9-2 



8-9 



7-2 



9-4 



6-5 



73 



10-0 



9-9 



On the east coast there are during the year 165 days on which rain falls ; 

 on the west coast there are 212 days on which rain falls. The greatest 



