41 
1921.] New Zealand Institute Science Congress. 
The Geology of Western Samoa, by Dr. J. Allan Thomson. 
Abstract. 
With the exception of coral-sand plains, a few feet above sea-level in various parts, 
and a cemented beach sand around the beaches, the rocks of Western Samoa are all 
of volcanic origin. The volcanoes have not quite ceased their activity. The known 
eruptions are Mauga Afi, about a.d. 1760 ; Manua Group, 1866 ; Mauga Mu of Aopo, 
1902 ; and Matavanu, 1905 to 1913 . The remainder of Savaii mostly consists of young 
lavas and ash-cones, the latter arranged mainly along a longitudinal west-north-west 
to east-south-east fissure, which continues across the Apolima Strait, through the islands 
of Apolima and Manono and right through Upoln. The latter island is much more 
eroded in the eastern end, and the volcanoes have been much longer extinct. 
The Structure of the Mangahao No. 1 Gorge (Mangahao Hydro-electric 
Scheme), and its Bearing on the Construction of the Proposed Dam, 
by G. L. Adkin. 
The Warped Land-surface of the South-eastern Side of the Port Nicholson 
Depression, by Dr. C. A. Cotton. 
The Great Barrier Island, by J. A. Bartrum. 
The Geology of the Port Waikato District, by Rev. Brother Fergus 
(T. M. Gilbert). 
Abstract. 
South of the Waikato Heads occurs a folded older mass of Mesozoic age, on the 
broadty truncated erosion surface of which was laid down a younger mass of Tertiary 
strata, showing unconformity, or at least discontinuity of deposition, between some 
series, as at the Kawa Stream. North of the Waikato River is an area of younger 
Quaternary sedimentary strata with a line of elevated sand-dunes fronting the coast. 
Along lines of major dislocation coincident with the northern limit of the Manukau 
Harbour in one case, and, in the other, with the line of the lower Waikato River, 
considerable differential movements resulted in the uplift of the areas to the north and 
south relatively to the middle, or Manukau, area. The latest considerable movement 
of the southern area appears to have been an uplift to the approximate height of 180 ft., 
and to have occurred since the Waikato River began to discharge itself by its present 
outlet. This estimate is based upon the data furnished by the pumice-bed in the 
section exposed south of Kawa Stream. Minor oscillations have occurred in subrecent 
times, especially in the middle area. The Manukau sand-dune range originated in a 
spit or barrier beach which created a broad estuary of the Waikato River. The 
Manukau Harbour owes its origin to streams, during minor uplift, cutting into silts 
deposited in the former Waikato estuary, whilst subsequently the area subsided 
slightly, allowing the sea to penetrate into these stream-courses. The ages of the 
Tertiary strata and the importance of the physical unconformity and strati graphical 
discontinuity in the Kawa beds cannot be decided definitely without further palaeonto¬ 
logical evidence, which, it is hoped, will be available in the near future. 
The Tertiary Geology of the Awamoho District, by G. H. Uttley. 
A Ball and Pillow Lava from Hawaii, by Dr. J. Allan Thomson. 
PHYSICS, CHEMISTRY, AND ENGINEERING SECTION. 
Presidential Address : Electric-power Supply in New Zealand, by L. 
Birrs. 
Abstract. 
Dealing with the cost of electric-power plants, the author said that the legisla¬ 
tion under which electric installations may be established in New Zealand, based on 
the assumption that the majority of the plants would be publicly owned, was exceed¬ 
ingly simple, and the legal procedure cheap compared with that of Great Britain and 
elsewhere. With regard to the future, the Government proposals provided for one 
horse-power for each five head of population—say, 240,000 horse-power for the whole 
Dominion. The normal coal-consumption for the Dominion was about 2,500,000 tons 
per year, and the possible saving in coal-consumption, averaging both city and country 
