Vol. 54.] TEACHTTE PE031 CLIPPERTON ATOLL. 233 



DiscTJSSiois' (on the two peeceding Papees). 



Prof. Clowes stated that, as a chemist, he felt nmch interested in 

 Mr. Teall's paper. He assumed that the Author intended it to be 

 understood that a double decomposition took place between the 

 ammonium-phosphate solution derived from the guano and the 

 insoluble aluminium silicate of the rock ; in that case, ammonium 

 silicate would pass away in solution, and no deposition of silica would 

 take place in the rock. Erom a chemical standpoint, the Author 

 had fully proved an extremely interesting case of chemical meta- 

 morphosis. It reminded the speaker of a somewhat analogous 

 instance of chemical change, which he discovered in conjunction with 

 Prof. Blake some years since in the neighbourhood of Nottingham. 

 There a rock containing barium carbonate had apparently undergone 

 change into barium sulphate, by the action of water containing 

 calcium sulphate ; this change was known to take place, but in the 

 above instance the change lacked the satisfactory proof given by 

 the present Author. 



Dr. Blanford said that he could not agree with Admiral Wharton 

 that the facts as stated are incompatible with subsidence. Neither 

 a volcanic crater with a distinct rim, nor a lava-flow, such as the 

 phosphatized trachyte appeared to have been originallj-, could be of 

 submarine origin ; nor was it probable that either originated on a 

 level with the surface of the sea. It was more likely that both 

 crater-rim and lava were formed above the sea, and had been 

 depressed. 



Mr. Clement Heid asked what climatic conditions held on this 

 island — was it a rainless area, or one with alternate rainy and dry 

 seasons ? 



Capt. Stipfe observed, with reference to the question of climatic 

 conditions raised by the previous speaker, that he believed deposits of 

 guano could be accumulated only in a comparatively rainless district, 

 as in rainy localities the guano would be washed away as quickly as 

 deposited. 



Prof. Hull and Mr. Batjeeman also spoke. 



Sir A. Geikie, in reply to the remarks made by previous speakers, 

 said that he unfortunately possessed no information regarding the 

 meteorology of Clipperton Atoll. He could see no reason why 

 a volcanic crater should not be formed below the surface of the 

 sea ; but the Clipperton crater may have been of the same explosive 

 origin as that of Santorin, and its solitary rocky peak may be the 

 only remaining visible fragment of its rim. With regard to the 

 supposed impossibility of lavas having flowed under the sea, he 

 could only observe that no facts in the geological history of Britain 

 were more abundantly proved than that from the earliest Palaeozoic 

 periods the vast majority of the volcanic eruptions in our region have 

 been submarine, and that they have included the outflow of lava, the 

 solid, unbroken sheets of which are now found intercalated between 

 strata full of marine organisms. 



Mr. Tball also replied. 



