ARTHUR'S PASS TUNNEL.

Manawatu Standard, Volume XLI, Issue 8538, 19 March 1908, Page 3

ARTHUR'S PASS TUNNEL.

SCIENTIFIC RESEARCH. EARTH'S HEAT GRADIENT. The big tunnel under Arthur's Pass, which will join Canterbury and Westland, will give .scientific men in Christchurch an opportunity for making interesting; and important researches, and the council of the Canterbury Philosophical Institute is making preparations for carrying out. operations as soon as the contractors have commenced the immense hole in the hill. The council has sot up a Tunnel Committee,consisting of Drs. Coleridge Fan- and Halgcndorf, and Messrs E. G. Hogg and R. Speight, who have drawn up a scheme of work which it is hoped will be taken in hand with the assistance of the contractors and the Government. The committee's principal object, says the Times, is to ascertain the earth's heat gradient in the tunnel. The most difficult operation will be the determination of the mean temperature of the surface of the earth's crust, above the tunnel. This will bo done by establishing miniature meteorological stations over the pass, and sinking thermometers to a depth of about 6 feet in the solid rock. The thermometers will form a line along the whole course of the tunnel's length of live miles and a half, and the observations will have to be recorded every fortnight in good weather and bad. Severe snowstorms sweep over the Alps in the winter, and this work will often be accompanied by much discomfort, and perhaps some hardship. Great ;caro will have to be exorcised in taking these records, as they will be watched for with keen interest by scientists in all parts of the world.

i Bores will also be made in the walls of the tunnel running in about 6ft at intervals of 200 yds from end to end. Thermometers will be placed in these bores, and the temperature of the rocks will bo recorded. By comparing the readings of the. surface above the tunnel and the readings inside the tunnel, the earth's heat gradient will be determined. The highest temperature recorded in the Swiss tunnels was 104 degrees Fahrenheit in the Siniplon. Mr Speight expresses an opinion that the temperature in the Arthur's tunnel will not rise to more than 60 or 70 degrees, and there arc circumstances which will probably keep the temperature down. The beds of rock lie mostly on their edges. They dip on high angles, to use the geologist's term, and a great deal of water will come down the bedding plains, reducing the temperature considerably* The surface of the ground in the pass is naturally wet, owing to the continual melting of the snow, and this also will have an effect on the heat gradient. The extraordinary variations of heat in some of the Swiss tunnels are attributed to the pressure from the earth's movements. These will not bo expected in the new tunnel, as the New Zealand Alps are a.n .ancient range, and most of the stress caused by earth movements was satisfied very many years ago.

Other investigations will also be undertaken by the Christchurch scientists. The.y will make eollections of the rocks found in the work of constructing the tunnel, and a good idea will be supplied by the specimens of the mctho'd of formation of tho New Zealand Alps. As f:ii" as is known, the rocks will be mostly slides and sandstones, and gray waeke. It is not likely that they will yield results of economic importance, although beds of graphite may be found, as this mineral occurs in the locality. The rocks have been very br.rren ns far as fossils are concerned. If fossils arc found, much importance will be attached to them, as they will enable the age of the rocks to be stated with some kind of certainty. Mr Speight says that it is rather regrettable that the core of the great range lies nearly 40 miles to the west of tho site of the tunnel, which will pierce only the eastern flank of the portion of the ranges. This fact has robbed the tunnel of some interest which is nttached to tho Swiss tunnels, as they practically pierce ihe actual core. Mr Speight believes that tho granite rocks between Taipo and Kumara probably, represent the constrtictural centre of the central Alps. Their great age is shown by tho few waterfalls they carry, and they have none whatever of great size.