410 Notices of Memoirs— Professor Alexander Agassiz — 



physiognomy of the coast. I am at a loss to understand the state- 

 ments of Ortman i-egarding the reefs of Kaneohe Bay on the north 

 shore of Oahu. The accurate observations of Hartt and of Eathbun 

 on the moderate thickness of coral reefs off the coast of Brazil seem 

 to have escaped Heilprin and Ortman, as well as other writers on 

 coral reefs. Eathbun has described the reefs along the Brazilian 

 shore, and finds them all as ' having very little height, but from the 

 surface looking like massive structures.' Hartt and Eathbun have 

 described the formation of extensive coral patches and the mode of 

 building up columnar masses which may eventually reach the 

 surface forming mushroom- or even bell-shaped structui'es, of which 

 enlarging rims may meet, ' resulting in the formation of a connected 

 reef surface supported by many upright pillars underneath 

 from forty to fifty feet high,' the so-called ' chapeiroes ' of the 

 Portuguese. These patches frequently occur near the shore along 

 the margin of a fringing reef, but are best developed in the deeper 

 water of the Abrolhos regions and between these and the city of 

 Bahia, growing upon the submerged rocky ledge. The number of 

 reef building corals in Brazil is quite small, and Nullipores seem, 

 according to Eathbun, to play a very important part in the building 

 up of the limestone reefs. 



" Professor Bonney summarizes the position of the theory of coral 

 reefs as now left (1889) in the following terms : ' That this theory 

 may have been expressed in terms a little too comprehensive, that 

 there may be a larger number of exceptional cases than was at first 



supposed, is quite possible It may very possibly be 



found that, as remarked by Mr. Bourne, the history of coral reefs 

 is more varied and complicated than was at first supposed, but it 

 seems to me that, as the evidence at present stands, it is insufficient 

 to justify a decision adverse to Mr. Darwin's theory as a general 

 explanation.' 



" Professor Bonney, in spite of his intention to present an ab- 

 solutely unbiassed expression, has, in common with most geologists 

 not familiar with coral reefs, retained the view of the correctness of 

 Darwin's theory. It can scarcely be said that the earlier examinations 

 of coral reefs were made with the detail which has characterized the 

 later explorations. The original work of Darwin was limited to 

 a narrow field, and supplemented by data derived from charts and 

 descriptions. Its correctness depends wholly upon the existence of 

 masses of coral reefs of great thickness, where coral reefs exist as 

 barrier reefs or atolls, and having assumed this the rest naturally 

 followed. For no one will deny that subsidence is one of the 

 possible modes of formation of masses of limestone of great thickness. 

 But subsequent observers showed most distinctly that both atolls 

 and barrier reefs occurred in regions of elevation. These exceptions 

 are not limited to a single area. They occur in regions of the globe 

 widely separated. While it undoubtedly is true, as remarked by 

 Professor Bonney, that Darwin has noticed most of the causes on 

 which stress is laid by his critics, it should also be remembered that 

 Darwin did not observe the phenomena subsequently examined, 



