126 REPAIRS—TUNNELS. 
An engine-house for, say, 7 engines, costs, with turn-tables, about.....--.-.-.- $3,500 00 
A common way-station house, about..-...-.-+------+--------++--- es $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. 
“Tt 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 almest any sub- 
stance, from granite rock to quicksand, and therefore the nature of the ground can hardly be said ° 
to oppose any other obstacle than that occasioned by the cost.” 
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 646 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 11} 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 33 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 run out 
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, 
