July 19, 1900] 



NATURE 



28- 



air, fresh water, a telephone in each direction out, a medicine 

 chest, barometer and thermometer. 



The cost of the tunnel was about 3,000,000/., or 220/. per 

 yard, and occupied ten years in construction. 



The temperature in the middle of the tunnel remains nearly 

 constant, summer and winter, and is about 19° to 20° C. = 66° 

 to 68° Fahr. 



The altitude of the tunnel is 4248 feet above sea-level, and 

 the height of the mountain above the tunnel is 5428 feet : the 

 temperature of the rock is greatly influenced by this latter fact. 



The question of the temperature of the rocks passed through 

 in the construction of a tunnel is one of great interest, as it 

 depends upon several conditions : (i) the character of the rock ; 



Fig. 5. 



2000 



800 



MC MOUNTAIN AaOVI / / 



HE SIMPLON TUNNIL / / 



MONT CENIS^'^:' ARLBERa 



GOTMARD^ 



•00 



CVBVES SHOWING DEPTHS C0BBE8P0ND- 



lua TO AN Increase in Temperature 

 OP 1° C. FOR THE Mont Cenis, 

 Gothard and Arlberg Tunnels. 



(With curve of probable temperature for the Simplon Tunnel.) 



(2) the inclination of the beds — those which attain a vertical or 

 nearly vertical position being less able to confine the heat than 

 those which are more or less horizontal ; (3) the height of the 

 mountain above the tunnel, or in other words, the thickness of 

 the blanket. 



A diagram is shown (Fig. 5), giving the temperature actually 

 encountered in the St. Gothard and Arlberg Tunnels, and from 

 these, aided by the carefully prepared geological section along 

 the centre line of the Simplon Tunnel, an approximate line is 

 given of the temperatures which are expected. 



The possibility of cooling the rocks and the air of the tunnel 

 will be dealt with later on, but there is in addition a permanent 

 lowering of the temperature after the tunnel is complete, 



NO. 1603, VOL. 62] 



particulars of which will be given under the description of the 

 St. Gothard. 



For each 144 feet of superincumbent rock or earth the increase 

 is found to be 1° Fahr. 



The St. Gothard Tunnel. 



This, which is at present the longest railway tunnel in the 

 world, is 9*3 miles in length, and constitutes the summit of the 

 "Gothard bahn," that is, the railway which runs from Lucerne 

 to Chiasso near the Italian frontier. 



The altitude of the tunnel at its north portal is 3639 feet, and 

 at its south portal 3757 feet above the sea. A gallery of direc- 

 tion was driven throughout, and the gradient of the rails is only 

 such as to provide for efficient drainage, viz. 5*82 per thousand, 

 or about i in 172. 



The following table may be of interest, giving the result of 

 investigations as to the cooling of the rocks. 



Temperature of the Rock in the St. Gothard 

 Tunnel. 



Above are Centigrade. 



Although the works were carried on with energy, and with all 

 the best appliances then known, the time occupied was ten 

 years ; but the most serious feature of the work was the heavy 

 mortality amongst the men : no less than 600 deaths occurred, 

 including those of both the engineer and contractor. 



From the experience then gained, great improvements have 

 been introduced into the works of the Simplon, as will be de- 

 scribed later on ; but the heavy loss of life in the St. Gothard was 

 due to insufficient ventilation ; the high temperature ; the ex- 

 posure of the men to the Alpine climate after emerging 

 from the tunnel ; the want of care as to the changing of the 

 men's wet mining clothes ; and the poor character of the food 

 with which the men supplied themselves. All this has been 

 greatly ameliorated, and even in English tunnels certain im- 

 provements have been introduced, which were brought from 

 Switzerland. 



The traffic through the tunnel has so largely increased that the 

 question of ventilation became of pressing importance, and the 

 system of Signor Saccardo, the well-known Government in- 

 spector of railways and engineer of Bologna, has been installed, 

 which is an ingenious application of the injector system. One 

 of the first introductions of this method was in the case of the 

 Pracchia Tunnel, on the main line between Florence and 

 Bologna, through the Apennines. This is a railway of single 

 line, and was built many years ago by the late Mr. Brassey. 

 There are 52 tunnels in all, but those on the eastern side are of 

 comparatively little importance. On the western slope the 

 gradient nearly throughout is 25 per thousand (or i in 40), and 

 it is here the greatest difficulty exists. There are several tun- 

 nels whose lengths approximate to icoo, 2000 and 3000 yards, 

 and the traffic is both heavy and frequent, the locomotives very 

 powerful, with eight wheels coupled. 



Under any conditions of wind the state of the longest tunnel 

 is bad, but when the wind is blowing in at the lower end at the 

 same time that a heavy goods or passenger train is ascending the 

 gradient, a state of affairs is produced which is almost in- 

 supportable, and one might as conveniently travel in a furnace 

 flue. 



