28 
elsewhere. Nevertheless the wells increased in number. To 
explain this phenomenon it was surmised that the lavas were 
disposed in layers, partly porous and partly impermeable, thus 
affording' the same alternation which had yielded the favorable 
results in the stratified rocks. Usually there was a succession of 
earth, clay, limestone or coral, and the ' water gushed forth 
when a solid rock floor was reached. Coupled with the discov- 
ery of Tertiary fossils, it is now possible to propose a new theory 
of the artesian conditions in agreement with the early demur at 
the notion of the origin of the streams of water from lavas. 
Extinct species of mollusca of the genera Osfrea, Chama, 
Conns and Purpura demonstrate the Tertiary age of the beds en- 
closing them. In the railroad cut near Waipio to the west of 
Pearl City is a solid bed of oyster shells a foot thick, belonging 
to the extinct species Osfrea rctusa, interstratificl with sands 
and clays. The limestones near Diamond Head yield many shells 
and corals of the same age. The formation indicated is the 
Pliocene. Until now it has been currently stated that the Ha- 
waiian Islands were the very latest geological product, entirely 
post-Tertiary. The picture is drawn of a volcanic vent at the 
iDOttom of the sea, discharging lava and gradually building up a 
basaltic cone upon w^hich corals flourished and made reefs. 
There is no reason to change the nature and order of this 
process, except that the beginning of this w^ork is set back some- 
wdiat earlier in time. That will enable us to add considerable 
to our geological history, and render possible the discovery of 
mineral deposits, such as beds of clay and earthy iron ores, 
which have been already pointed out. 
Summarizing the data, I have indicated the presence of a 
terrane of Tertiary deposits upon Oahu, between Koko Head 
and Barber's Point, underlying several famous sugar plantations, 
besides the city of Honolulu, and extending more or less entirely 
around the island, rising as much as 300 feet above the sea level. 
For the sake of definiteness I have given the local name of 
Pearl Harbour Series to these deposits, perhaps 1,000 feet thick, 
consisting of sands, conglomerates, clays, limestones and sundry 
volcanic products, all resting upon a hard basaltic floor. The 
elongated dome of Koolau, on the east, may be compared to the 
roof of a house over which rain flows abundantly upon either 
side and percolates the porous sediments, yielding artesian flows 
when pierced by the drill. Owing to the copious rainfall flow- 
ing wells will be found all over the productive belt next the sea 
shore. A contour map of this floor based upon the positions of 
the water-yielding layer will show the presence of channels more 
or less corresponding with the existing valleys. At the begin- 
ning of the period of deposition Oahu stood as much higher 
than now as is indicated by the depths of the wells, and the slow 
depression predicated corresponds to the growth of the coral 
