ioo St. Helena. paet i. 



Yon Bucli has described a compact limestone at 

 Lanzarote, which seems perfectly to resemble the sta- 

 lagmitic deposition just mentioned : it coats pebbles, 

 and in parts is finely oolitic : it forms a far-extended 

 layer, from one inch to two or three feet in thickness, 

 and it occurs at the height of 800 feet above the sea, 

 but only on that side of the island exposed to the violent 

 north-western winds. Von Buch remarks, 1 that it is 

 not found in hollows, but only on the unbroken and 

 inclined surfaces of the mountain. He believes, that 

 it has been deposited by the spray which is borne over 

 the whole island by these violent winds. It appears, 

 however, to me much more probable that it has been 

 formed, as at St. Helena, by the percolation of water 

 through finely comminuted shells : for when sand is 

 blown on a much exposed coast, it always tends to accu- 

 mulate on broad, even surfaces, which offer a uniform 

 resistance to the winds. At the neighbouring island, 

 moreover, of Fuerteventura, 2 there is an earthy lime- 

 stone, which, according to Von Buch, is quite similar 

 to specimens which he has seen from St. Helena, and 

 which he believes to have been formed by the drifting 

 of shelly detritus. 



The upper beds of the limestone, at the above- 

 mentioned quarry on the Sugar-Loaf Hill, are softer, 

 finer-grained and less pure, than the lower beds. They 

 abound with frasrments of land-shells, and with some 

 perfect ones ; they contain, also, the bones of birds, and 

 the large eggs, 3 apparently of water-fowl. It is pro- 

 bable that these upper beds remained long in an uncon- 



1 * Description des Isles Canaries,' p. 293. 



2 Idem, pp. 314 and 374. 



3 Colonel Wilkes, in a catalogue presented with some specimens 

 to the Geological Society, states that as many as ten eggs were found 

 by one person. Dr. Buckland has remarked (' Geolog. Trans.' vol. v. 

 p. 474) on these eggs. 



