AGASSIZ: BEKMUDAS. 221 



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

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

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

 port on the Bahamas, page 170, wliei-e 1 have given an abstract of the 

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

 whicli 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." ^ Yet it is on observations gathered in a district thus 

 characterized by him tliat Heilprin bases his assent to tlie Darwinian 

 theory of coral reefs, and he dissents from those wht) 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 ccolian charac- 

 ter of the I'ocks of the Bahamas and Rernmdas. This chai'acter saute 

 aux i/eax in every dii'ection. In the Bahamas the vertical clilfs of the 

 weatlier side of tlie islands show this to perfection, and here and there a 

 quarr}^ 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 ])Ossil)le intermediate ele- 

 vations. Tlie rock everywhei'e ])i'esonts the same structure. There are 

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

 lent exposures of the a'oliau strata twisted and turned in every possil)le 

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

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

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

 surfice of these Eeolian rocks has liecome indiu'ated by the percolation of 

 fresh water tln-onuh its mass, and has formed here and there the thin 

 riim'ing coating so comiiiou all over tliose islands, where the surface is 

 not so well protected by v(>getation as it is in tlie Beinnudas. Thi-ough- 

 out the islands avc come upon evidence of the extensive denudation 

 and erosion which have affected the a-olian rocks of the islands and 



1 Bernuula Islands, p. 40. 



