ARTHUR'S PASS TUNNEL

Star (Christchurch), Issue 9253, 4 June 1908, Page 4

ARTHUR'S PASS TUNNEL

— * — SCIENTIFIC INVESTIGATIONS. THE PHILOSOPHICAL INSTITUTE'S WORK. There was an exceptionally large attendance at the meeting of the Canterbury Philosophical Institute last evening, when two lectures were given on subjects dealing with the Arthur's Pass Tunnel. The Council of the Institute has drawn up >a scheme of investigations, largely on the lines of those adopted in connection with the great Swiss tunnels, and it is expected that as the boring takes place some i very valuable general and local knowledge will be obtained. Mr E. G. Hogg, president of the Institute, who presided at the meeting, gave the first address. He dealt with the laws that govern the distribution of heat in the interior of the earth, and showed what investigations have been made in that respect, and what might be done at the big tunnel. He eaid that determination of the rate at which the temperature rose as investigations went further towards the centre of the earth, was very difficult. Investigations made in that respect in tunnels were free from sources ol error that showed themselves in mines and deep bores, but even in tunnels the existence of hot or cold springs, and the quantity of radium found in the rocks pierced by a tunnel might make it very difficult to decipher tho records obtained. The accumulation of tunnel observations of temperature might eventually throw considerable light on the structure of a mountain chain and the manner in which the mountain mass was related to the interior of the earth. In order to ascertain the surface rock temperature, the observation stations would be selected as nearly as possible over the line the tunnel would take. At each station, a vertical hole, six feet deep, would be drilled in tho solid rock, to hold a hollow iron tube, in which a slow-reading thermometer would be placed. These thermometers would be read each fortnight, and from the records obtained in this manner over a space of three or four years, the rock-temperature at a depth of about six feet from the surface would be plotted, and its value, free from the disturbing periodic variation, would be determined. It would be the first occasion on which work of that nature was attempted on any serious scale in New Zealand. Within the tunnel bore-holes would be drilled at distances of two hundred yards from each other, in the side of the tunnel, as near as would be safe to the advancing face of the tunnel. The bore-holes would be six feet deep, slightly inclined to the horizon, to allow any water percolating into them to escape. Slow-acting thermometers, for the most part, would be used, but in certain of the bores maximum and minimum thermometers would also be inserted. After a suitable time had elapsed to allow of the dispersion of the heat generated by the boring tool to be dissipated, the thermometer would be placed in position and the hole securely stopped with rock and Band. Readings Avould be taken at the end of 24, 48 and 60 hours after the first insertion of the thermometer. The Institute had good reason to believe that it would secure a dories of accurato observations, which would be of great scientific vnlne. It had been assured of the cordial co-operation of Messrs M'Lean Brothers, the contractors for the tunnel, in oprrying out the scientific work successfully. Dr C. Coleridge Farr, who dealt with radio-activity, pnid tfrnt the boring of the tunnel would supply opportunities for comparing the tpmpornture Gradient «»nd the radio-active contents of fhe rocks encoiinterprl in the work. The discovery of rndio-ncHvitv had opened nn a new book in r»hysi<\s. and when Curie discovered that radium maintained itself at a temperature above its surroundings it was clear that that was a cause of the maintenance of the earth's and the sun's internal heat. Elimination showed that sufficient radium, and more, existed in the rocks to account for the effects. The temperature ?r» dient had not heen cer- | tflinly established, and +he radium contents of many and •wide-spread specimens of rocks hnd not been FmffifiVr>+ly examined, and it was in th.-»t direction that tV>e investigations at the Arthur's Pasc Tunnel miVht be exneoted fr> throw lio-lit on important onop.tinns. Onp invpefcifator. St»'Titt,.. hnd e^l^ulatprl t^at tho don+li to which the radium found +<y evist in the rocks mmt o-o to cive sufficient heat to account for t^e temnpratirre grndiont. could not extend to more than tHrtv-flvn mil^s. Tn that ease the centre of tho ea^th rraa at » r*nnst.ant t orr> nerr>tiire of pKnnt, irifWTpo 1 C^-ntifrrr>do. Tt was infeve^+infr to note that consideration of tV>n speed of ■nronflfnt'OTi of earthonnke waves fl-> t<->ti <tYi +lip pnrti' fravo rip" to flip r»onrd'ision th°t, t.^o character of +hp. ea roll's interior altered at about forty miles down. At! ftflrlrocq on the frpolr\rr\^n] ■^•o»"V Jif the tunnel hnc? hnp.n prer»ovo/> Tw T\fr R. P-noiorirf;. hut it 'V^s flnoirWT that a T*-hole eve-nine: ontrl->t to be rrivon up to the. nd^' o**.0 **. which was set down for next meet^T