October 27, 1904J 



NA TURE 



629 



small fragment of rock falling on to the permanent 

 way. 



In order that the present condition of the work may 

 be better understood, a longitudinal section along the 

 line of the tunnel is given, drawn to a small scale; 

 and, with a view to illustrate the facts better, the 

 gradient is very considerablv exaggerated. 



It will be noticed that the gradient rises from each 

 end of the tunnel towards the middle, the object of 

 which has been to provide efficient drainage from the 

 face, and it is an instance of the prudence which 

 has been exemplified throughout the entire work that 

 this system was adopted from the commencement. In 

 driving a heading forward under a mountain, it is a 

 matter of very common occurrence that springs of 



prevent delay, this was done for some considerable 

 distance ; but in consequence of a hot spring being 

 encountered at the " face " on the Swiss side it was 

 deemed necessary to withdraw the workmen, and the 

 tunnel between points A and B has become filled with 

 hot water. 



At each end of the tunnel — Brigue at the north 

 portal, and Iselle at the south or Italian entrance — a 

 large and well equipped installation is provided for 

 carrying on the works, and each of these is provided 

 with machinery of sufficient capacity and power to 

 serve for half the distance, that is, to the summit of 

 the tunnel at \. 



The work of actual perforation at Brigue and Iselle 

 began in .-Xugust, 1898, by hand, and by Brandt drill 

 in December, 1898. When, however, the advance from 

 the Italian entrance had reached a point between 15 

 and 16 kilometres, the great spring of 12,000 gallons 

 per minute was encountered. This caused a delay of 

 several months, thus throwing back the progress very 

 considerably. In the meantime, the advance from 

 Brigue proceeded rapidly, the summit A being reached 

 in the month of December, 1903. Then arose the 

 question, as already explained, in order to save time, 

 of driving the tunnel downhill in order to meet the 

 workmen coming up from Italy. 



Meanwhile, the work on the Italian side has been 

 pushed forward until the distance remaining to be 

 pierced, as alreadv mentioned, is only some 260 yards; 

 but a serious difficulty has arisen, for again a hot 

 spring has been encountered, and the temperature of 

 the rock in the advance gallery is 108° F. 



The system adopted for dealing with hot springs 

 is very ingenious — and at the same time very simple. 

 It was at first proposed to conduct the hot water out 

 of the tunnel through pipes, but the simpler and more 

 efficient method, which was adopted, is to play a jet 

 of cold water into the fissure from which the hot water 

 is escaping, and thus to cool it down to such a degree 

 that the workmen are not seriously incommoded ; they 

 are then able to continue the drilling and blasting. 



A channel or canal is being excavated at one side of 

 the tunnel to carry the hot water from the spring to 

 the outside, and this will be covered over with non- 



SwiTZERLAND I ITALY 



TOTAL LENGTH 19 730 "I" 

 L^UGTH STILL REM/:tNING TO BE PIERCED . B . 2G0 YARDS. 



Fig. 4. — Longitudinal section of Simplon Tunnel. 



water are encountered; consequently, on the ascend- 

 ing gradient, the water flows away by gravity from 

 the workmen; but should the work be carried out»on 

 a descending gradient, then the water accumulates 

 where the men are working, not only causing them 

 inconvenience and delay, but requiring to be pumped 

 out over the highest point of the rails. In order to 



NO. 1826, VOL. 70] 



conducting material to prevent the heat rising into 

 the tunnel. 



The question arises from whence this great heat 

 comes, for although observations made in various wells 

 and borings in all parts of the world give an approxi- 

 mate figure of 1° F. rise in temperature for each 70 

 feet of vertical depth, this is insufficient to account for 



