126 REPAIRS TUNNELS. 



An engine-house for, say, 7 engines, costs, with turn-tables, about $3,500 00 



A common way- station house, about $1,500 00 



REPAIRS AND INSPECTION OF TRACK. 



It is generally the case, on our roads, that one man carefully inspects about two miles of track 

 every day. He makes all the small repairs that are necessary. 



By the use of hand-cars, from five to ten miles of track could be daily inspected and repaired 

 by one party. 



TUNNELS. 



&quot; It is a rule which may be regarded as generally applicable, that to make a cutting more than 

 sixty feet deep would be costlier than to bore, unless the material is required for a neighboring 

 embankment. Economy is the principal test in these matters; for in the present advanced 

 stage of engineering, a tunnel may be made of almost any length, and through almost any sub 

 stance, from granite rock to quicksand, and therefore the nature of the ground can hardly be said 

 lo oppose any other obstacle than that occasioned by the cost.&quot; 



There is, however, an instance of an excavation 110 feet in depth in sand. 



Shafts are usually sunk along the line of the tunnel at from 500 to 1,000 feet apart. On the 

 Blaisy tunnel one shaft is 046 feet in depth; on the Nerthe tunnel one of 610 feet. 



It is now a quite generally received opinion that shafts are not so necessary for the ventilation 

 of the tunnel after its completion as was formerly supposed to be the case. Where it was pro 

 posed to use machinery for excavating, a tunnel of 7.5 miles miles has been projected without the 

 use of shafts. 



Shafts are usually from 7 to 11 feet in diameter. 



The largest tunnel of which I can find a record is one in the district of Schemnitz, in Hungary. 

 Its length is variously stated at from 10 to ll miles. It is used to drain an extensive series of 

 mines, and also for the transportation of ore on railway cars. 



The longest tunnel of large dimensions which I find recorded as having actually been com 

 pleted is one in France. It is 3^ miles long, and a little more than 26 feet in diameter ; 54 shafts 

 were employed. 



The section of railway tunnels varies considerably in different countries and on different 

 roads. The dimensions of several will be found in the tables which follow. 



Several machines for the excavation of tunnels have been invented. It does not appear that 

 any of them have proved successful ; so that in estimating the time necessary to construct any 

 proposed tunnel, it will be safer to base the calculation upon the results of works actually com 

 pleted. 



As a general thing, headings, as they are called small tunnels in fact are first driven 

 through, and afterwards enlarged, to form the large tunnel. This method of proceeding has 

 great advantages in some localities, but is not always resorted to. 



The grades can be so arranged in railway tunnels as to facilitate the drainage during the con 

 struction by establishing a summit in the middle of the tunnel, thus allowing the water to runout 

 at each end without interfering with the work ; there are instances of great embarrassment 

 caused by the neglect of this simple precaution. 



In France there are 56 tunnels on railways; eight canals, 36 of which have an aggregate length 

 of 45.4 miles. The longest of small size is 7.45 miles, and that of large dimensions 3.5 miles. The 

 Rouen and Havre road has eight tunnels; Paris and Lyons also eight. 



The aqueduct from the Durance to Marseilles has three tunnels, whose aggregate length is 10.5 

 miles. 



That through the Taillades had 7,320 gallons of water pumped out per minute during a part of 

 the time it was under construction. 



