TUNNELS. 



709 



tliis road had been attempted by no road up to that 

 time ; and even yet the running expenses and freight 

 charges are higher than they would be with lower 

 grades. On this account the project of the tunnel was 

 still considered seriously even alter the canal had been 

 abandoned. In 1848 the Troy and Greenfield Rail- 

 road Company was incorporated with the object of 

 building a road through the mountain. The most 

 eminent geological authority of that day, Prof. Ed- 

 ward Hitchcock, of Aiiiherst College, examined the 

 mountain, and stated that quartz and mica slate were 

 the chief substances to be encountered. In 1851 the 

 work upon the tunnel was commenced with a clumsy 

 and expensive boring machine, which attempted to 

 bore a hole of the full size of the tunnel. When this 

 and similar machines had proved failures the work was 

 abandoned until 1X54. The State of Massachusetts 

 then loaned $2,000,000 and took a mortgage on the 

 property of the companyassecnrity. From this source 

 funds were obtained until 18fi2, when the work, again 

 stopped, and the State foreclosed the mortgage. The 

 State having committed itself to the work commis- 

 sioners were appointed to oarry it on. but on account 

 of its slow progress the State, in 18(18, made a con- 

 tract for its completion. At that time the work was 

 in the following condition : East end, 52S:i feet ; west 

 end, 4055 feet; west shaft sunk to grade, 318 feet, 

 and central shaft sunk to a depth of 583 feet. The 

 contract required the completion of the additional 

 15,743 feet, the central shaft to be sunk to grade, and 

 the sum to be paid, $4.5',)4,2(>8. The work was suc- 

 cessfully prosecuted; and on Feb. 9, 187"). the first 

 railroad train passed through the lloosac Mountain. 



Down to Isi'i") the drilling and blasting had been 

 done by old methods ; after that date the State com- 

 missioners used machine-drills driven by compressed 

 air, as had been successfully done in the Mont Cenis 

 tunnel under the Alps. For using compressed air suf- 

 ficient water-power was obtained at the east end ; while 

 the central and west end sections were carried on with 

 steam-power. The first drills were heavy and expen- 

 sive ; and later a less complicated and lighter machine, 

 with a gang of drills, was used. With this machine a 

 hole of from 4 to 5 feet in depth could be made in ;m 

 hour ; and one of the drills was kept running for over 

 3 months without the slightest repair, during which 

 tinii' the total depth of holes drilled would have meas- 

 ured over a mile in length. The compressed air was 

 stored in a tank and conveyed to the tunnel through 

 12-inch iron-pipes carrying a pressure of about <>0 Ibs. 

 to the square inch. A rubber-pipe, easily discon- 

 nected when the drill-carriages were taken out of the 

 way of a blast, connected the iron-pi|>e8 with the 

 drills. A heading, 8 feet high by 24 feet wide, was 

 driven by the first gang. About 500 feet in the rear 

 of this another gang was employed in enlarging the 

 tunnel to the full size of 22 by 24 feet. The average 

 number of men employed was from 500 to 800, and 

 136 lives were lost during the construction. Work 

 was carried on continually night and day, with the ex- 

 ception of Sundays. Down to 1805 the chief explo- 

 sive was the ordinary black powder ; but after that 

 date nitro-glycerine was used for a short time, and it 

 was finally decided to use trinitro-glycerine manufac- 

 tured upon the spot. The central 1 shaft, located near 

 the centre of the tunnel, is 1028 feet deep. This was 

 sunk not only as a ventilator, but also as a means of 

 shortening the time of the work by allowing other 

 gangs to work cast and west from its bottom. After 

 sinking to the tunnel-grade an advance was made to 

 the west of 2006 feet, and to the cast of 1503 feet. 

 But so much water poured into the tunnel that it is 

 doubtful if much time was saved in this way. After 

 the sinking of the central shaft it was thouirlit best to 

 sink a shaft toward the western entrance, on account 

 of the uncertain structure of the rock in that part of 

 the tunnel. This also helped to shorten the time of 

 the work. After the tunnel hud been projected monu- 



ments were built upon the points of the two highest 

 summits overhead. The transit instrument threw 

 these monuments in line and extended the line in 

 either direction for several miles. This not only fur- 

 nished the line upon which the tunnel was constructed, 

 but also the line by which the central and western 

 shafts were sunk. When the headings from the cen- 

 tral shaft and from the eastern opening came together 

 their alignments swerved from each other by only -fa 

 inch ; whereas, the opposite arms of the Mont Ceuis 

 tunnel had a divergence of more than half a yard. 



The tunnel cost the State of Massachusetts, with 

 interest on the investment, about $18,000,000; but 

 t lie cost would not have been so great had the im- 

 proved methods of machinery and blasting been used 

 earlier in the progress of the work. The first plan for 

 the use of the completed tunnel was to allow all rail- 

 roads to have equal rights ; but this was soon aban- 

 doned, and special privileges were given to one line. 

 After several years. of unsatisfactory dealing the State 

 of Massachusetts, in January, 1887, completed the sale 

 of the Hoosac tunnel, with the accompanying 44 miles 

 of railroad, to the Fitch burg Railroad Company for 

 $5,000,000 in bonds and $5,000,000 in stock of the 

 railroad. 



In June, 1888, a tunnel was opened through the 

 Cascade range in Washington Territory. The work 

 was begun in April, 1886; the material and machinery 

 were hauled in wagons for over 90 miles through a 

 rough country without roads; some of the heavy ma- 

 chinery was moved by block and tackle the whole dis- 

 tancc. and $125.000 had been expended before the 

 actual work began. The tunnel is 9850 feet long and 

 16 feet wide by 2()J feet high in the clear. It is in- 

 tended for a single-track road. The west end approach 

 consists of an open cut through trap-rock, while the 

 east end enters the tunnel by crossing a creek imme- 

 diately under a cataract, which has a fall of IfiO feet. 

 Before crossing this creek the track is made by cutting 

 a heavy ridge or slide of earth and loose rock. These 

 two approaches contained in the aggregate upward of 

 30.000 eublic yards of material, most of which was 

 solid rock, requiring to be blasted. The strata or forma- 

 tions of the mountain lie nearly flat, having but a 

 slight inclination from east to west across the entire 

 range. This increased the danger and difficulty of the 

 work. The rock throughout was a gray conglomerate 

 basalt of medium hardness, but slacking and scaling 

 on exposure to air, rendering timbering necessary. 

 The work was constantly prosecuted from both ends 

 with the most approved machinery ; one of the air 

 compressere was run by water-power, and the other by 

 steam. The tunnel was run without the use of air- 

 shafts. 



Tunnels for mining purposes are less frequent than 

 railroad tunnels. They are used to reach deposits of 

 gold and silver, and also to drain the mines. One of 

 the more recent enterprises is the Big Bend tunnel of 

 Butte co. , Cal. Certain points in the valley of the 

 Feather River having been found to be unusually pro- 

 ductive of gold, it was considered niost desirable for 

 economy's sake to connect these points. To this end 

 a tunnel was commenced in 1K82, and completed in 

 1887. It practically diverts at will the whole of the 

 river from its present channel, and carries it through 

 a mountain. Six gates of iron and steel, each 4J by 

 8 feet, at the head of the tunnel, control the passage 

 of the water. The size of the tunnel is 12 by 16 feet, 

 and the length is over 2 miles. 



Hirer Timneh. Small tunnels -under navigable, 

 streams are quite frequent in the United States. In 

 Chicago a number have been bored under the Chicago 

 River in order to connect the several parts of the city 

 without bridges. The project of a tunnel under the De- 

 troit, Itivcr, through which railroad traffic should be car- 

 ried without interfering with navigation, has long been 

 discussed. Various towns have, from time to time, 

 been selected as sites for the beginning of operations. 



