138 IV. rnysicAL geography. 



Orkney Isles, off the north coast of Scotland. The out- 

 lying group of Shetland Isles will carry the range of lati- 

 tude considerably farther northward ; making the total 

 range about eleven degrees, between the latitudinal 

 lines of 50 and 61 ; small fractions disregarded. The 

 full range of longitude may be called ten degrees ; al- 

 though nowhere is that width attained under the same 

 parallel of latitude. The oblique position of the island 

 and its islets, which throws almost the whole of Scotland 

 on the western side of the longitudinal line which divides 

 England into nearly equal halves, increases the range of 

 longitude in proportion to the actual width. The more 

 easterly longitudes of England thus become represented 

 only by sea to the northward of latitude 53. This pecu- 

 liarity renders it difficult to trace out any easterly ten- 

 dencies of the jplants. The few species restricted to the 

 most easterly longitudes are also thus necessarily plants 

 limited to the most southerly latitudes. Again, they are 

 plants peculiar to the distant lowland, as opposed to the 

 mountainous tracts ; and also they have certain seeming 

 geologic relations, whether purely accidental or causal. 

 It is thus difficult to say with which of these geographic 

 conditions they are in real relation or causal connexion. 



2. Extent and Area. — The measurement from extreme 

 south to extreme north of the main island, by the longest 

 line, is stated to exceed 600 miles ; the line crossing 

 wide indents of the sea in parts of this length. The longest 

 line that can be drawn over land, without crossing any 

 considerable inlet of the sea, runs from Rye, in Sussex, 

 northward or north-westward to Cape Wrath, in Suther- 

 land ; and this line is said to measure 580 miles. The 

 longest transverse line, running in a direction from south- 

 west to east or north-east, is traced from the Land's 



