238 THE PLANT WORI.D 



the northern half of the island with the volcanic outcrop of Santa Rosa, 

 the cliflFs bounding the west coast of the northern half, the terraces one 

 encounters on the road from Agaiia to Yigo, and the occurrence in various 

 places of funnel-shaped sinks Uupog) in the coralliferous limestone. I 

 then described the volcanic mountains of the southern part of the island 

 across which General Wheeler and I passed the other day, the smooth, 

 slippery, naked surface of the red earth contrasting with that of the 

 verdure-clad northern region, and the deeply cut river valleys. I also 

 spoke of the disappearance of certain streams on the island, of the cavern 

 in the Talofofo valley from which the river issues, and Matan-hanom, the 

 lake which is the source of the Agaiia River ; and I described the broad 

 coral flats and barrier reefs along the west coast of the island, with their 

 level floor of fine coral sand. 



Mr. Agassiz said that Guam is perhaps the most interesting island 

 which the Albatross has visited, combining as it does elevated coral- 

 liferous limestone platforms and volcanic outcrops, together with coral 

 reefs in process of formation. The general features of the island recall 

 those of Nine, Eua, and Makatea. With the exception of Viti Levu and 

 Vanua lycvu, of the Fiji group, Guam is the largest island encountered 

 on the cruise. I had heard that it was Mr. Agassiz 's object in making 

 this cruise to gather evidence to disprove Darwin's theory of the forma- 

 tion of atolls and coral reefs ; but after hearing him tell of his observa- 

 tions I felt convinced that he was only seeking the truth irrespective of 

 any theory. He spoke with great respect of Semper's work in investi- 

 gating the coral formations of the Pelew group, but he does not agree 

 with Darwin and Dana in their theory, that subsidence has been the 

 great factor in the formation and growth of coral reefs in general. Too little 

 importance, he thinks, has been attached to the forces causing the denuding 

 of elevated coral islands and to the part played by submarine erosion. Mr. 

 Agassiz thinks that many atolls were originally raised platforms of coral, 

 and that they have been cut down gradually, sinks having been formed in 

 them like those on this island, surrounded at first by high rims and after- 

 wards cut into islets, with passes between them leading from the ocean into 

 the enclosed sound. He thinks that barrier reefs have also been formed in 

 very much the same way. On leaving he said that he would send his 

 assistant. Dr. Mayer, to call upon me. The Governor invited him to 

 stay at the palace to-night, but he declined, saying it had been his rule 

 to sleep on board the ship during the entire cruise. 



In Mr. Agassiz's preliminary report on the scientific results of the 

 expedition he describes the northern half of Guam as an irregular mesa 

 of limestone "cut by deep crevasses, full of pot holes and sinks." In 

 reality the mesa is so regular that a cart may be driven over it, and much 

 of the coral comprising it is little modified. 



