50 THE entomologi.st\s record. 



the extracts quoted will, I believe, help me to make clear m}- 

 argument. 



I have already given a brief summary of the general 

 meteorological and climatic conditions of the Continent, and 

 shown the limited extent of melanism existing there. I would 

 now turn to our own country and examine its peculiar climatic 

 and meteorological conditions, and compare them with those 

 of the Continent. The following appear to be the chief points 

 to which attention should be directed : — 



(i). The first thing that we must notice is the fact that our 

 climate is strictly insular, with an average temperature of 

 40*^ to 60° F., with very few extremes of either excessive heat 

 or cold. On the Continent great extremes are registered.^ 



(2). The meteorological, conditions of our Islands are 

 governed almost entirely by the influence of the Gulf Stream. 

 This Stream, which is a warm current with an average 

 temperature of 30° F. above the surrounding ocean, is a 

 branch of the Atlantic equatorial current. After passing 

 round the Gulf of Mexico, the Gulf Stream runs round 

 Florida into the Atlantic Ocean, skirts the eastern coast of 

 the United States for some distance, and then strikes off in 

 a north-westerly direction across the Atlantic towards Britain 

 and Scandinavia, As I have stated, its temperature is 

 generally much higher than the surrounding ocean, hence 

 there is always a great deal of vapour rising from it. This 

 vapour, therefore, affects the atmosphere over this current, 

 and renders it moist and humid. 



(3). The prevailing winds in Britain are from the south-west. 

 These winds blow over the Gulf Stream ; hence in their 

 course they become exceedingly humid, and laden with moisture 

 before they strike our western shores. 



(4). The easterly winds, which blow from the icy plains of 

 Siberia, are so extremely cold that almost all the moisture has 

 been condensed before they cross the Continent of Europe. 

 The North Sea is too narrow to modify them to any very 

 great extent ; hence they strike on our shores as dr}^, piercing 

 winds, and thus affect our eastern coast in a contrary direction 



' In Keith Johnston's Physical Geography, pp. 52 and 53, we find: — " Our 

 climate in the British Isles is a decidedly maritime one ; its average temperature 

 ranging from about 40° F. to 60" F. In Central Asia, however, in the same 

 laiitude, and at the same height above the sea, the average temperature ranges 

 from about o*^ F. in winter to about 70*^ F. in summer. The temperature of the 

 British Isles surrounded by the sea thus varies only 10° on an average during the 

 year, but that of the centre of the Continent in the same latitude changes to the 

 extent of 70^." 



