1905-1906.] FormatioTi and Flora of a Shingle Island. 291 



happened. Map I. is copied and enlarged from the Ordnance 

 Survey map drawn in 1870: and Map II. shows the same 

 stretch of the river, as nearly as I have been able to give 

 it from roug.h sketches made on the spot. There are doubt- 

 less inaccuracies in this map, but the general proportions are 

 correct. I made no drawings of the right and left banks of 

 the Orchy east of the middle of Eilean a Phortaire ; and 

 those two outlines (which I have copied from the Ordnance 

 map) may now be slightly different. It will be noticed that 

 the altitude of the fields is 133 feet; that of the island itself 

 ranges from 127 to 133 feet. 



Forty or fifty years ago the river-banks were carefully pro- 

 tected, and the Orchy ran through Dalmally Vale in a com- 

 paratively narrow channel, with hardly a shingle bank in 

 its course. At that time Eilean a- Phortaire had already 

 assumed its present appearance, but the island immediately 

 to its west was a mere shingle bank, very little overgrown. 

 The two are now continuous, and at first glance appear to be 

 one large wooded island of uniform age ; but the junction is 

 very clearly seen on visiting the island. Map I. shows these 

 islands in an intermediate stage. 



As recently as twenty-four years ago, the fields on the 

 northern river-bank extended much farther south ; and our 

 Shingle Island was then a comparatively narrow strip of 

 gravel, cut in two by a small stream, and level with the 

 fields, from which it was separated by the main body of the 

 river. When proprietors grew careless and left off protecting 

 the banks, these fields received the full force of the current* 

 and a large curve has now been cut away from them. The 

 river is still eating farther and farther into them ; and great 

 lumps of turf and sand are continually being undermined, 

 and may be seen dropping down all along the edge of the 

 bank. About eleven years ago the rough breakwater above 

 mentioned was built ; and this has diverted the current, and 

 retarded, though it has not stopped, the wearing away of the 

 banks. The diverted current has since swept the gravel to 

 right and left, piling it up both on our Shingle Island and 

 in the bay immediately opposite on the south. Seven years 

 ago this bay was full of water, but it is now completely filled 

 up with gravel, as shown in Map II. 



