XV. 



lONA, 1st December 1852. 



Immediately after I had despatched my last letter to you I went 

 out for a short sail and saw several Black Guillemots in various 

 states of plumage. I shot the whitest, and on examiaation it 

 reminded me of what I had forgotten to remark — namely, that the 

 tail of this Guillemot, like its wings, does not change colour in 

 winter, but remains black. This is only the case with the tail 

 feathers, for the upper and under coverts change colour, getting 

 tipped with grey or becoming actually white. 



I also killed a Great Northern Diver {Colynibiis glacialis) 

 weighing between eleven and twelve pounds. The day was very 

 calm and the water perfectly smooth. My companion and I 



