426 Transactions. 



The accompanying graph gives the rock-temperature for three miles and a 

 half from the Otira end, the observations being taken every 5 chains for the 

 first 45 chains, and thereafter every 10 chains. No readings were taken at 

 tlie Bealey end. Since it was desired to correlate the temperature-readings 

 with the overburden of rock, the basal temperature line (9° C.) on the 

 graph has been given the same slope as the tunnel-floor. It will be noted 

 that the temperature graph is roughly parallel to this basal line, and that 

 the minor variations in it, amounting to 3° or 4° C, show no sign of 

 parallelism with the overburden of rock. The capricious variations shown 

 are due chiefly, if not entirely, to the rate at which the water near by 

 percolated from the surface or from the seams in which it was lying. That 

 some heating effect was produced by the passage of this water through 

 the rocks is, however, apparent from the fact that the average temperature 

 of the wet rocks in the tunnel is about 10° C, while the water in the 

 surface streams is about 45° C. 



Temperatures were read twelve, twenty-four, and forty-eight hours 

 after the insertion of the thermometer, but in only four out of the thirty- 

 five holes put in was there any difference among the three readings of 

 the same hole. The greatest variation shown was at the hole at 1 mile 

 55 chains, where the readings were 13°, 12-9°, and 12-8° C. 



Biology. 



The only observation of biological interest was the growth of the fungus 

 known as Armillaria mellea on the temporary timbering of the tunnel, 

 where it formed great pendulous bunches of mycelia about 3 ft. long, and 

 somewhat similar in size and appearance to a horse's tail except that the 

 individual strands were coarser. Only the vegetative form of the fungus 

 was found, and this was found only on the jjine timbers of the Otira end, 

 being absent from the eucalyptus props of the Bealey end. Probably the 

 fungus occurs in the bush whence the timber was cut and the spores are 

 carried in when the props are placed in jjosition, where the equable 

 temperature, the moisture, and the darkness provide suitable conditions 

 for vigorous growth. The estimated minimum rate of growth is about 

 3 ft. in a year, but this has been noticeably altered by the completion 

 of the bore, the constant aeration having produced greatly accelerated 

 development. 



The Committee wishes to express its sincere thanks to the Right Hon. 

 Sir Joseph Ward, who, as Prime Minister, made a grant in aid of the 

 expenses of the investigation ; to the Hon. G. W. Russell for permission 

 to publish the report in the Transactions of the New Zealand Institute ; to 

 Messrs. McLean Bros, (the original contractors for the tunnel) and to the 

 Public Works Department for facilities for making the observations recorded ; 

 and especially to Mr. A. Dinnie, Engineer in Charge, for his unfailing 

 courtesy and willing assistance, and to Mr. Manson, underground foreman, 

 for making most of the temperature observations. 



