THE CRAIG OF AILSA. 121 



the most friendly disposition appears to exist. Immediately adjoining this 

 division, and to the north is the principal situation occupied by the Guil- 

 lemot for hatching. 



The character of the rock here suddenly changes, from the shattered 

 appearance it presents amongst the Geese, to that of a more massive and 

 solid nature, along which a series of ridges, averaging from ten to fifty feet 

 in length, and varying in height from fifty to five hundred, and seldom 

 exceeding six inches in breadth; on these ledges the birds are so closely packed 

 that it would be difficult to introduce the hand betwixt them, and no idle 

 or barren bird is countenanced by this industrious community. As the Com- 

 mon Guillemot is the bird to which my observations principally apply, I 

 would remark that, with the exception of the Solan Goose, it is the earliest 

 bird which arrives at this breeding station. They begin to appear about the 

 1st, of April, and if a westerly wind should prevail, they have nearly all 

 returned by the 4th.; there are also other arrivals about this time, to which 

 I shall probably refer on some future occasion. The Guillemot builds no 

 nest, and not even one fragment of sea- weed or any other material is provided 

 by the bird, to ensure the egg, (for you are aware they only lay one,) from 

 rolling ofi" the uncertain position in which it is very frequently placed; and when 

 the birds are driven from their nests, or eggs rather, from a shot being fired 

 amongst them, the exposee of eggs is about one of the most interesting 

 sights to be witnessed upon the Craig, and the Naturalist looks with astonish- 

 ment at the endless variety before him; for I am persuaded that from out 

 of one thousand dozen, not two eggs could be found alike, and I question 

 much if ever two were; this does not arise from any difference in the formation 

 of the egg, but from the variety of markings and colouring, which you will 

 find illustrated in the specimens before you. The Guillemot, as I remarked, 

 lays only a single egg about the middle of May, and as the young one becomes 

 pretty well fledged about the 15th. of July, she then carries it on her back 

 about that time into the sea. It has been a matter of much conjecture with 

 me how such a wonderful difference should exist in the colour of the eggs, 

 considering that the food and habits of the birds are precisely alike; and as 

 I have not yet been able to reconcile this, I attribute it wholly to some 

 physiological cause, which, I have little doubt, can be explained by some of the 

 members better skilled in the science than myself. If I recollect properly, 

 I think the late Professor Wilson, during a tour through the western islands, 

 remarked the variety, and thought that it might occur to enable every bird 

 to distinguish its own egg; and from this being a very reasonable supposition, 

 I feel inclined to support his opinion. If this bird, however, had provided 

 itself a nest, I might think otherwise, but from the indiscriminate manner in 

 which the eggs are placed, and that so close to each other, I consider it a 

 very judicious arrangement for each bird to have its own private mark. 



The egg of this bird is larger in proportion to the bird than any other 

 I have ever seen. The eggs of all the aquatic birds found at the Craig are 



