The Republican journal. [volume] (Belfast, Me.) 1829-current, 1872-12-26
Remarkable Engineering

When the first opening from the Cen
trail shaft to the east end OF the HoOsac
Tunnel was opened on Thursday, 10Th
inst, it was known before any measure
ments had been made, that the error. if
any. in direction WAS very small. The
hole was enlarged, and the lines carried
through from the shaft to the end on Sun
day last, and the total error was found to
be but fire sirtee,Hhs Of an inch literally,
and one and q quarter inches in level, the
depth being measured from the top of .
mountain Only those who appreciate
the enormous difficulty of carrying line
into a tunnel where no compass is worth
its weight in old iron as guide, but es-
pecially the exceeding delicacy Of the
process of carrying down one thousand
feet perpendicularly similar points, can
understand how great Il triumph this mar
vellous accuracy was. We venture to say
that no great work of the kind was ever
done by keener eyes or steadier hands, or
was more patiently, carefully and fire.
quently verified, and the result reflects the
brightest credit upon all concerned. The
following communication from the con-
sulting engineer of the State will be in
teresting in this connection =
A correspondent in describing the join
ing of the headings at the Hoosac Tunnel
said the discrepency in the working lines
"could not be much over a foot and might
be very much less" Having taken the
first possible opportunity after clearing
away of the smoke, l visited the tunnel,
and, with Mr.. Frost and his assistant en-
gineers, spent II day in connecting the
line, with the view of making such mod-
fication as necessity might require. | was
the first man to measure the discrepancy
after the points had been fixed from the
west at the place of meeting, and found
it to be lust five sixteenths Of an inch of
lateral error.
The vertical amounts to one tenth of
a foot, or one and a quarter inches, nearly,
ascertained by comparing the inside levels
with the levels which were run over the
mountain in 1870 by Mr.. Frost. The sue
cess of this as an application Of the exact
science depends more upon the persistent
industry of the engineering corps than
upon any new methods employed. The
| project OF definite direction from the
bottom of shaft, where magnetic direc-
ton is useless, is no new problem, but [ dc
| not remember of another instance where a
| horizontal line has been so exactly extend
ed for a distance of over fifteen hundred
feet (over a fourth of mile) from the
bottom of smoky pit over a thousand
feet in depth and only twenty three feet in
diameter Nor another instance where q
tunnel had been cnt with such exactness
for taoo and quarter miles from its portal
without communication with the surface.
The processes are old in their essentia
parts, but the detail has been worked out
by endless patience on the part of the
whole engineering corps. Amid falling
rocks and sutfocating smoke, surrounded
by the most depressing circumstances OF
danger, darkness. filth and monotonv
those men have plodded on day after day
and month after month for the past years
with none of the exhileration which at
tends ordinary field work in the open air.
1t may be satisfaction to all who have a
hand in it to meet with such success.
wish it to be known that American
engineering is not behind the rest of the
world in precision, where such result
can be obtained by skill and patient in.
dustry, and think the result will be APP
preciated by all lovers Of exactness.