ANIMALS INTRODUCED FOR AMENITY 291 



establishment in certain definite areas which have become 

 centres of colonization for the surrounding districts. 



The spread of the Squirrel, as also the steps of its dis- 

 appearance, have been minutely worked out by Dr Harvie- 

 Brown in a series of three papers published' in 1 880 and 

 1 88 1 in the Proceedings of the Royal Physical Society of 

 Edinburgh, and to these I would refer readers desirous of 

 knowing the details of the early movements, contenting 

 myself here with a general survey, carried down to the 

 present date, of the results of the various introductions. 



Fig. 53. Common Red Squirrel a former native of Scotland. 

 reintroduced. \ nat. size. 



It may be premised that the spread of the Squirrel was 

 not equally rapid in all the areas, that it was regulated in 

 direction as well as in speed by the physical characters of 

 each district as well as by the state of its woodland ; bleak 

 mountains, and to some extent, rivers, obstructed or checked 

 the onward movements, while close-set woodlands acted as 

 stepping-stones, guiding and hastening the progress into 

 new districts. Reference to Map III will aid in the compre- 

 hension of the influence of the different centres, and of the 

 direction and speed of the various migrations. 



192 



