214 A NATURALIST ON DESERT ISLANDS. 



the old male, but somewhat duller. On the pectoral 

 region a broad dusky band extends across the 

 breast on each side, but does not meet in the middle 

 line. Distinctly scarce as compared with the next to be 

 described. 



(3) Young males and females. Head, nape and upper- 

 parts black, rest of plumage as in No. 2. Bill, pale- 

 bluish-grey, light lavender-blue at base ; iris sepia- 

 brown ; legs and webs pale flesh-coloured ; gular sac 

 (not distensible) pale lavender-blue. These birds made 

 up the great bulk of the colony. 



(4) Some few birds, apparently older males than those 

 of No. 3, had orange gular sacs, and in some the white 

 under-parts were mottled and becoming darker, as if 

 preparatory to turning uniform black as in the quite 

 old males. 



Almost directly after leaving this little plateau, we 

 crossed a narrow razor-edge, from which the ground fell 

 precipitously on either side to the sea, a matter of three or 

 four hundred feet. Here one of our party, completely 

 exhausted by the heat and the lack of breakfast, which 

 he had been unable to get before leaving the ship, had to 

 cry enough, and we left him under the shade of a bush. 

 On the other side of this edge was a steep talus slope, 

 strewn with angular fragments of rock, splintered and cast 

 down from above, by the alternate expansion and con- 

 traction which occurs during the intense heat of the day 

 and the subsequent cooling during the night. The 

 rock of which Orquilla is composed is a species of granite 

 called diorite, and it was interesting to notice the different 

 effects of weathering here as compared with the kind met 

 with on Blanquilla (biotifce). 



In crossing this slope, we were startled to hear shrill 

 raucous cries proceeding from the holes and crevices 

 immediately beneath our feet, and in another minute we 

 became aware that we had stumbled upon a nesting colony 

 of boatswain-birds (Phaeton cethereus). Had it not been 

 for their cries, caused by the noise of our feet stumbling 



