306 Branner — Geology of the Hawaiian Islands. 



The east hase of Diamond Head, — In an article published 

 in vol. xi of the Bulletin of the Geological Society of Amer- 

 ica, pp. 57-60, Dr. Dall speaks of certain beds at the base of 

 Diamond Head on the island of Oahu. It is possible that my 

 own observations about the eastern base of that mountain were 

 not made upon the same beds as those spoken of bv Dr. Dall, 

 but as nearly as I can make out from the text of liis article, 

 the beds are the same. If so I do not agree with some of his 

 conclusions in regard to geologic structure. He says: "It 

 (Diamond Head) is composed of horizontal layers of tiijff, inter- 

 stratified with thin layers of calcareous sand, the lime from 

 which, leached out by the rain, is redeposited in a thin super- 

 ficial crust of a brilliant white, giving the effect, among the 



The section exposed beside tlie road at the southwest base of Diamond Head. 



sparse arid vegetation, of a thin layer of snow. The strata of 

 the head have not the ' onion peel ' aspect of layers of succes- 

 sive subaerial eruptions, but are strictly horizontal and have 



every aspect of having been deposited in water My 



observation w^as not carried to a point more than 100 feet above 

 the sea-level, but it is evident that the sand layers occur, inter- 

 stratified in the mass, clear to the top (TOO feet). The upper 

 limy layers appear, so far as observed, to be composed almost 

 entirely of calcareous sand, and no shells or corals were observed 

 in them in a recognizable state. At about 50 feet above the 

 sea the heavy tuifs overlie the uppermost heavy layers of calcar- 

 eous rock. The latter is nearly or quite horizontal, and consists 

 of coral-sand grains more or less compactly consolidated, with 

 occasional patches where marine fossil shells were abundant. 

 There are hardlv traces of coral larp-er than fine o-ravel and no 

 coral masses." 



