1832.] THE BOOBY AND THE NODDY. 23 



origin ! In its hardness and translucency — in its polish, 

 equal to that of the finest oliva-shell — in the bad smell given 

 out, and loss of colour under the blowpipe — it shows a close 

 similarity with living sea-shells. Moreover, in sea-shells, it 

 is known that the parts habitually covered and shaded by 

 the mantle of the animal, are of a paler colour than those 

 fully exposed to the light, just as is the case with this 

 incrustation. When we remember that lime, either as a 

 phosphate or carbonate, enters into the composition of the 

 hard parts, such as bones and shells, of all living animals, 

 it is an interesting physiological fact* to find substances 

 harder than the enamel of teeth, and coloured surfaces as 

 well polished as those of a fresh shell, reformed through 

 inorganic means from dead organic matter — mocking, also, 

 in shape some of the lower vegetable productions. 



We found on St. Paul's only two kinds of birds — the booby 

 and the noddy. The former is a species of gannet, and the 

 latter a tern. Both are of a tame and stupid disposition, 

 and are so unaccustomed to visitors, that I could have killed 

 any number of them with my geological hammer. The 

 booby lays her eggs on the bare rock ; but the tern makes 

 a very simple nest with seaweed. By the side of many ot 

 these nests a small flying-fish was placed ; which, I suppose, 

 had been brought by the male bird for its partner. It was 

 amusing to watch how quickly a large and active crab 

 {Graspus), which inhabits the crevices of the rock, stole 

 the fish from the side of the nest, as soon as we had dis- 

 turbed the parent birds. Sir W. Symonds, one of the few 

 persons who have landed here, informs me that he saw the 

 crabs dragging even the young birds out of their nests, and 

 devouring them. Not a single plant, not even a lichen, 

 grows on this islet : yet it is inhabited by several insects 

 and spiders. The following list completes, I believe, the 

 terrestrial fauna: a fly {Offersia) living on the booby, and 

 a tick which must have come here as a parasite on the 

 birds ; a small brown moth, belonging to a genus that 

 feeds on feathers ; a beetle {Quedius) and a woodlouse from 



* Mr. Horner and Sir David Brewster have described (" Philosophical Trans- 

 actions," 1836, p. 65) a sinffiilar "artificial substance resembling shell." It 

 is deposited in fine, transparent, highly polished, brown-coloured laminae, 

 posbessinsT peculiar optical properties, on the inside of a vessel, in which 

 cloth, first prepared with glue and then with lime, is made to revolve rapidly 

 in water. It it much softer, more transparent, and contains more animal 

 matter, than the natural incrustation at Ascension ; but we here again see 

 the stronff tendency whidi carbonate of lime and animal matter evince to 

 form a solid substance allied to shell. 



