176 bulletin: museum of comparative zoology. 



I do not find that Mr. Alexander Agassiz mentions the precise process 

 by which the aeolian deposits were hardened, but it seems quite evident 

 throughout his paper on the Bermudas ^ that he thinks the sands are all 

 calcareous, of organic origin, and cemented on land by rain-water, after 

 having been blown up from the shores. Verrill lays stress upon " the 

 secondary infiltration ... of calcium bicarbonate and the deposition of 

 calcite," and he notes that "this zone of calcification " would always be 

 higher than high tide-level.^ 



Jukes mentions the cementation of such calcareous sands by rain- 

 water* in Australia, and Dana speaks of similar phenomena on the 

 Hawaiian Islands.* 



" At King George's Sound in Australia . . . the upper layers . . . 

 have been hardened by the action of rain on the friable calcareous 

 matter, and the whole mass has originated in the decay of minutely com- 

 minuted sea shells and corals." ^ 



Many cases have been noted of the consolidation of beach sands by 

 ocean spray blowing over them. On the island of St. Croix mention is 

 made of shells and other substances, including iron utensils on shore, 

 having spray charged with calcareous matter dashed over them. " These 

 generally unite and harden, especially near the surface, and form into a 

 tolerably compact mass." ® Evidently the hard rocks are in process of 

 formation. 



The only analyses seen of the beach-hardened calcareous sandstones 

 are those given by the writer. These are of the aeolian sandstones of the 

 islands of Fernando de Noronha. They show those rocks to contain, in 

 one case, 98 per cent of lime carbonate and less than one per cent of 



1 A visit to the Bermudas in March, 1894. Bull. Mus. Conip. Zoul., XXVL, 

 No. 2. Cambridge, 1895. 



2 A. E. Verrill, Notes on the geology of Bermuda. Amer. Journ. Sci., 4th Ser., 

 IX., May, 1900, p. 321. 



Captain Vetcli, in Trans. Geol. Soc, 2d Ser., I., p. 172. London, 1824. 



On tlie calcareous sandstones of the Bermudas, see also Richard J. Nelson, 

 Trans. Geol. Soc. London, 1840, V., p. 103-123. 



A. Heilprin, The Bermuda Islands, p. 30-32. Philadelphia, 1889. 



J. Walter Fewkes, On the origin of the present form of the Bermudas. Proc. 

 Bost. Soc. Nat. Hist., 1888, XXIIL, p. 518-522. 



3 J. Beete Jukes, Narrative of the surveying voyage of the H. M. S. " Fly." 

 Vol. I, p. 9; 128; 339. London, 1847. 



* J. D. Dana, Corals and coral islands, ed. 3, p. 155. New York [1890]. 

 ^ Darwin, Geological Observations, ed. 2, p. 248. London, 1876. 

 6 S. Hovey, The Geology of St. Croi.Y. Amer. Journ. Sci., XXXV., p. 72. 

 New Haven, 1889. 



