286 The N.Z. Journal of Science and Technology. [July 
Report on the Natural Features of the Arthur’s Pass Tunnel, by F. W. 
Hilgendorf and others. 
(This paper will appear in the Transactions.) 
Press Notice (Lyttelton Times ). 
In 1908, when the Arthur’s Pass Tunnel was started, a committee of the Canterbury 
Philosophical Institute undertook to record the natural features exposed by the bore ; 
and, as the tunnel is now practically completed, Dr. F. W. Hilgendorf, convener of the 
committee, read a report on the observations at the Geological Section. 
The rock-structure, he said, was the same all the way through, varying from coarse 
grey to fine black slaty greywackes, and nothing new or interesting was disclosed. The 
temperature of the rock was taken every 10 chains, but the tunnel admitted such large 
quantities of water that the true rock-temperature was not obtainable, but only that 
of the percolating water. The great ingress of water was due to the faulted nature of 
the rock, many seams admitting up to a cubic foot per second. Those usually dried 
up in a few weeks or months, but there were still 7 cubic feet of water a second flowing 
from the tunnel-mouth. It was hoped to do some work on the radio-activity of the 
rocks, but that became impracticable owing to the inflow of water. 
A point of interest was the stalactites that had formed between the concrete blocks 
used for lining the tunnel. Those stalactites were about a foot long and as thick as a 
lead-pencil, and had, as true stalactites usually had, a hollow down the middle. Their 
rate of growth had been about 2 in. a year, whereas stalactites in limestone caves were 
stated to grow at the rate of about 1 in. in ninety years. The difference, doubtless, 
was due to the fact that the water dripping between the concrete blocks of the tunnel 
has calcium hydrate to work on, instead of calcium carbonate, as was the case in 
limestone caves. The final product, however, was the same in both cases, being pure 
limestone. The straightness of the tunnel and the fact that one end was 825 ft. higher 
than the other led to the expectation of a strong and constant upwards draught, but 
that had no! been foimd. There was usually a flow of air upwards from the Otira to 
the Bealey end, but sometimes that was absent and sometimes reversed. 
Range of Tertiary Mollusca in the Oamaruian of North Otago and 
South Canterbury, by J. Allan Thomson. 
Abstract. 
The Oamaruian is divided into five stages, four of which are marine at 
Oamaru and contain fossil molluscs. A very large number of fossils have 
been collected from the Oamaru, Waitaki, Waihao, Pareora, and Kakahu 
districts by officers of the Geological Survey and others, and have been 
determined by the late Mr. H. Suter. The plotted lists exhibited show the 
range of each species for each of these several localities. The majority of 
species found in the lowest, or Waiarekan, stage are also present in the 
highest, or Awamoan, stage, but there is a small proportion confined to 
single stages. This is particularly so in the case of the Awamoan stage, but 
the collecting, especially by Marshall in the Oamaru district, has been much 
more exhaustive for this stage than for any of the others. The difference 
in station of the species found in the Ototaran and Hutchinsonian probably 
accounts for the absence in these stages of many species common to the 
Waiarekan and Awamoan, and also for the presence of other species absent 
from the two last-named stages. The general result of the analysis is to 
show that the molluscan fauna did not change greatly during the Oamaruian, 
and hence distant correlations with individual stages based solely on 
mollusca are difficult to establish. A closer study of the fossils on 
evolutionary lines might lead to the discrimination of species now lumped 
together which might prove to have a zonal value. 
The Geology of the Middle Clarence and Ure Valleys, by J. Allan 
Thomson. 
(This paper will appear in the Transactions.) 
