AGASSIZ: BERMUDAS. 221 



I shall have occasion to refer to the views of Heilprin in the course of 

 the following pages. Regarding the statement he makes on the nature 

 of the Dolomitic reefs of the Tyrol, I would refer the reader to my Re- 

 port on the Bahamas, page 179, where I have given an abstract of the 

 views of the latest researches on the nature of the dolomitic reefs, views 

 which are diametrically opposed to those advocated by him. 



Heilprin says : " If it ever existed (the atoll condition), it has been 

 completely masked by overgrowth ; . . . the facts, such as they are, 

 show with sufficient clearness that the present islands and reefs have 

 little or nothing in common, beyond occupying position, with a pre- 

 existent ring." x Yet it is on observations gathered in a district thus 

 characterized by him that Heilprin bases his assent to the Darwinian 

 theory of coral reefs, and he dissents from those who hold opposite views 

 with a vehemence which might be excused in one having an extended 

 acquaintance with coral reefs. 



^OLIAN HILLS AND DUNES. 



Captain ^Nelson was the first to call attention to the seolian charac- 

 ter of the rocks of the Bahamas and Bermudas. This character saute 

 aux i/eux in every direction. In the Bahamas the vertical cliffs of the 

 weather side of the islands show this to perfection, and here and there a 

 quarry or a cut leaves no doubt that the substructure as well as the 

 superstructure of the island is all of the same character. On the Ber- 

 mudas one comes upon quarries of all sizes at all points, close to the sea 

 level or near the highest summits, and at all possible intermediate ele- 

 vations. The rock everywhere presents the same structure. There are 

 also endless rock cuts for the passage of roads (Plate IX.), giving excel- 

 lent exposures of the aeolian strata twisted and turned in every possible 

 irregular manner according to the direction of the then prevailing winds, 

 or we may come across a patch exposed in a cliff or in a deep cut where 

 the strata run parallel for quite a distance. As in the Bahamas, the 

 surface of these seolian rocks has become indurated by the percolation of 

 fresh water through its mass, and has formed hei-e and there the thin 

 ringing coating so common all over those islands, where the surface is 

 not so well protected by vegetation as it is in the Bermudas. Through- 

 out the islands we come upon evidence of the extensive denudation 

 and erosion which have affected the seolian rocks of the islands and 

 1 Bermuda Islands, p. 40. 



