BERMUDA". 19 



The sand is entirely calcareous and dazzling white when seen 

 in masses. When examined closely, in small quantities, it is 

 seen to consist of various-sized particles of broken shells. By 

 gathering samples from the shores where the material of which 

 the sand is formed is first thrown up, and selecting portions 

 where eddies of the wind have left the heavier particles together, 

 a sand full of large fragments of shell, and containing even many 

 whole shells of smaller species, may be obtained, and from the 

 examination of these an accurate conclusion may be arrived at 

 as to the main constituents of the finer more comminuted sand, 

 which is driven inland by the wind, blown up into the dunes, 

 and from which the whole island above water has been formed. 



The sand may be seen to be made up in by far its greater 

 part of the shells of Mollusca. Species of Tellina, Cardium, and 

 Area contribute most largely to compose the mass, together with 

 large quantities of pink-coloured fragments derived from a Spon- 

 clijlus, which is common about the islands. A few Gasteropodous 

 shells contribute fragments, and a considerable number of 

 Foraminiferous shells occur in the sand, and no doubt careful 

 examination would reveal the presence of fragments of tubes of 

 Serpulce, corals, calcareous algse, Bryozoa, and Cirrhipede shells ; 

 but there can be no doubt that by far the greater mass is derived 

 from the shells of Mollusca.* Thus, although the foundations of 

 Bermuda, and its natural breakwaters and protections, without 

 which it would not exist, are formed by corals, the part above 

 water is mostly derived from another source, and even below 

 the water the same is the case for some distance, for the same 

 beds of sandstone were met with in an excavation carried to a 

 depth of 50 feet. 



The shells, more or less broken, are thrown up upon the 

 beach, and there pounded by the surf. As the tide recedes, the 

 resulting calcareous sand is rapidly dried by the sun, and the 



* It would be of great interest to determine by careful microscopic 

 examination, what are the relative percentages of the very various cal- 

 careous structures composing the calcareous sands of coral islands in dif- 

 ferent parts of the world. I collected specimens of all the calcareous sands 

 accessible during the voyage of the "Challenger" with that object. They 

 vary very much in composition, some being mainly Foraminiferous. 



C 2 



