476 C. H. HITCHCOCK GEOLOGY OF DIAMOND HEAD, OAHU 



the precise localities which he investigated and on which he based his 

 conclusions. He was accompanied by Professor Edgar Wood, of the 

 normal school at Honolulu, who kindly pointed out to me the route taken 

 and the ledges examined. They did not visit Kupikipikio nor ascend 

 the cone of Diamond head, but skirted its eastern base, from whence it 

 was possible to see the white patches on the outer cliffs which simulated 

 ledges of limestone. I sent an account of my explorations and conclu- 

 sions to Doctor Dall, and received from him the following letter, which 

 is published with his sanction: 



"Washington, D. C, August 29, 1905. 



"Dear Professor: I received yours of the 22d instant this morning, and 

 was much interested in and gratified by it, as it seems to me that it leaves 

 hardly any unsettled points of importance in which I can not agree with your 

 conclusions. There are one or two questions of interpretation, perhaps, to be 

 presently referred to. You have been able, by reason of your more extended 

 explorations of the cone at the Head, to decide several questions I had to 

 leave open. 



"Doctor Bishop's idea is, as I understand, that Diamond head was the 

 product of a single outburst of activity, by which he may include the inter- 

 mittences which usually accompany the activity of a vent forming a cone 

 through the deposit of matter expelled at short intervals during a relatively 

 short period of time, say within a year or two. The impression I got was 

 that the cone was the product of small eruptions, with intervals between long 

 enough for coral sand beaches to form or sand to be deposited by wind on the 

 surface of ejected matter, so that there would be a certain alternation of 

 deposits ; also that this action, in part at least, took place near sealevel, with 

 some subsequent elevation. It seemed to me that the differences between the 

 Punchbowl (with little or no lime to be leached out) and Diamond head 

 (so to speak, saturated with lime) was due to somewhat such a difference in 

 method of formation. I can not otherwise account to myself for the abun- 

 dant presence of lime nearly throughout the Diamond Head cone. Does it 

 not seem, if the Bishop hypothesis be correct, as if the fragmentary lime 

 constituents dislodged by eruption must necessarily be concentrated in the 

 lower layers, so that, the vent once formed, there would be practically no 

 source for fragmentary lime rock for the upper ones? If not, why do we not 

 find fragmentary lime rock distributed through the layers of the Punchbowl 

 and other deposits of the volcanic hills behind Honolulu? That is the way I 

 summed it up, that in order to keep the supply of lime going there would 

 have to be, in the case of Diamond head, quiescent periods when it could 

 accumulate over or about the vent either from the sea or through the agency 

 of wind. Now down by the sea I found, as I thought, some thin, continuous 

 layers of lime rock on which were fossilized some corals, chamas, etcetera, 

 where they grew. I recognized the exudatory character of the sheets of lime 

 I saw on the cliffs above, but I took those near the sea to be sedimentary. If 

 in this I was mistaken, and they were also due to exudation, it does not alter 

 the general conditions very much. There must have been a source for the 

 lime somewhere, and after the vent was cleared, subsequent supplies must 



