CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 579 



of Mr Darwin was, in the opinion of Sir Charles Lyell,* the circumstance that, 

 as far as was known, no bed or formation of coral of any thickness had been 

 discovered. This objection, which was proposed by Mr Maclaren in 1842, 

 derives additional force at the present day in the light of my observations in 

 the Solomon Islands. 



(3) That these upraised reef-masses in the majority of islands rest on a partially 

 consolidated deposit which possesses characters of the " volcanic muds," which were 

 found during the " Challenger " Expedition to be at present forming around 



volcanic islands. 



(4) That this deposit envelops anciently submerged volcanic peaks. 



These two latter conclusions corroborate in a remarkable manner the views, 

 based on the observations of the " Challenger " Expedition, which Mr Murray 

 has advanced. I will cite the structures of two islands to illustrate these 

 views. In the small island of Santa Catalina I found that the elevated reef 

 was based on volcanic rock with the intervention of a thin brecciated 

 conglomerate. In the island of Treasury I found the volcanic rock covered by 

 a soft partially consolidated volcanic mud, which attained the thickness of some 

 300 or 400 feet, and was itself encrusted on the lower slopes of the island by 

 the elevated reef-mass. In the one island the volcanic peak had been first 

 exposed to breaker-action before the reef- corals established themselves. In 

 the other island the submerged volcanic peak was first brought within the reef- 

 coral zone by the deposition of layers of volcanic mud, assisted by the move- 

 ment of elevation. 



With reference to my own bias on this subject, I may here add that during 

 the first eighteen months I passed in the Solomon Islands I was only 

 acquainted with the theory of subsidence ; and that after having failed to make 

 my observations harmonise with the theory of Mr Darwin, I collected my 

 facts with a very confused idea of the direction towards which they were 

 tending. It was therefore a cause of great satisfaction to myself when I first 

 became acquainted with the views of Mr Murray. 



I will close this paper with a few remarks on the amount of elevation that 

 has occurred in this region in recent times. It is, however, difficult to gauge it. 

 So great has been the subserial denudation in these islands, that although the 

 elevatory movements have brought up to our view a deep-sea clay with its con- 

 cretions of manganese and a Foraminiferal limestone that was probably formed 

 in a depth of from 500 to 800 fathoms, two rocks which occur in islands 

 at opposite ends of the group, yet, notwithstanding this great upheaval, the 

 calcareous envelopes usually disappear from the slopes of the large volcanic 

 islands at heights of 500 or 600 feet above the sea, and never came under 

 my observation in such islands at greater elevations than 900 feet. In the 



* Principles of Geology, 12th edit., vol. ii. p. 612. 



