THE RAILWAY TUNNEL THROUGH THE ALPS. 163 
particles of dust from the drilled quartz and other rocks causes 
constant and considerable damage to the machines. This will 
be readily imagined when the number of blows, pushes, and 
revolutions made by the boring tools are enumerated. To 
bore eight holes 2f feet deep in the rock, when of average 
working quality, the motory cylinder completes 57,600 revolu- 
tions ; the striker, or driving piston, 57,600 blows ; and the 
chisels make the same number of turns or twists. 
As a matter of mere curiosity, to show the magnitude and 
extent of the various operations to be performed and labour 
required, it may be stated that if the above rates of working 
should be maintained, the number of holes necessary to be 
bored to get through the whole tunnel will amount to about 
1,600,000. The total depth of all these holes, when bored, 
will amount to about 4,265,890 feet, which is 105 times 
longer than the entire length of tunnel to be excavated. 
The number of blows required to be struck by the perfo- 
rators to do this work will reach nearly 13,000,000,000. 
It may be explained briefly, that the tunnel, for its whole width 
of face is not attacked at once, a gullet ” or heading is driven 
I considerably in advance of the completed work. This small 
gallery is rather more than 11 feet wide, and 7f feet high, and 
square in form. A line of rails is laid nearly the whole length 
of this gallery, of usual gauge, to communicate with the line 
in the main tunnel ; beside this, there is a line of rails of lesser 
gauge for the small trollies, used to convey the broken rocks 
from the head of the gallery to the common trucks. In 
general the machines which attack the front of this heading 
are armed with nine or ten perforators — some acting directly 
in the face, others diverging to the right and left, and thus 
carry on the borings in the gullet, till all the holes are ready 
for their charge of powder. Thirty-seven men and boys are 
required to attend to the machines, and other matters in con- 
nection with them. 
The work of the main tunnel follows up the small gallery, 
which is progressively widened to the extent and form 
required for the full section of the complete excavation. It 
has been estimated from data obtained by actual working of the 
machines, that the tunnel may possibly be excavated in fifteen 
years ; but it appears that twenty years is the time calculated 
upon by the engineers engaged in the conduct of the work. 
The limit assigned for the completion of the tunnel in the con- 
vention agreed between the French and Italian Governments, 
is twenty-five years. It is, however, a work requiring time, 
money, and patience ; it cannot be hurried, and must look to 
completion from steady and unremitting labour day and nighty 
without ceasing. 
