58 Ascension. paet l 



July, there was no remnant of the incrustation : but on 

 a point of basalt, from which the quarry men had lately 

 removed a mass of the calcareous freestone, the incrusta- 

 tion was perfectly preserved. Considering the position 

 of the tidal rocks, and the period at which they become 

 coated, there can be no doubt that the movement and dis- 

 turbance of the vast accumulation of calcareous particles, 

 many of them being partially agglutinated together, 

 cause the waves of the sea to be so highly charged 

 with carbonate of lime, that they deposit it on the first 

 objects against which they impinge. I have been in- 

 formed by Lieut. Holland, K.N., that this incrusta- 

 tion is formed on many parts of the coast, on most of 

 which, I believe, there are likewise great masses of 

 comminuted shells. 



A fron descent calcareous incrustation. — In many 

 respects this is a singular deposit ; it coats through- 

 out the year the tidal volcanic rocks, that project from 



No. 5. 



An incrustation of calcareous and animal matter, coating the tidal rocks at 



Ascension. 



the beaches composed of broken shells. Its general 

 appearance is well represented in the accompanying 

 woodcut ; but the fronds or disks, of which it is com- 



