The Somerset herald. [volume] (Somerset, Pa.) 1870-1936, 1884-10-15

All of the tunnels are being work
ed by compressed air drills, or prep
araiions are nearly completed for
their introduction. In the Sideling
Hill and Allegheny mountain Tur.
nels the electric light is used, the
first time We ever saw it adopted on
work of this nature. 1t is employ
ed mainly in lighting up the finish
ed tunnel, the deep shadows result
ing from it making oil lamps still
preferable at the working face. The
old-fashioned top-headiDg is the
rule among the contractors, the bot
tom.neading and side enlargement
adopted with such remarkable sue
cess III the piercing of the Arlberg
tunnel not yet having found favor
with American contractors. Very
considerable timbering has been so
far required, and the nature of this
| timber work is such as at once to
attract the attention of the engineer.
1t is permanent, to the extent of
about 7 years, and is located entire
ly outside of the proposed masonry,
permitting this last to be put in
place when suitable material can be
transported over the finished road.
Brick-yards, however, are being
started near several of the tunnels,
and the product will be largely used
on the line of the railroad, good
stone being exceedingly scarce over
many sections. The timbering in
place near the portals of the tunnels
presents an exceedingly neat appear
ance, and takes but minimum of
space outside the masonry. The sets
are placed about 80 inches between
centres usually, and they are tied
together longitudinally by 5x6 in.
ties, which are logged down 3 in.
over the arch timbers. The timber,
however, varies in design with the
character of the ground to be held !;
when very bad, the usual caps, posts
and rakers are employed.
The arched masonry upon the
line of the road, some of which is
started, attracts attention from the
peculiar form of the opening, which
is ovoid instead of full center or
segmental. This design has been
adopted after careful study by the
Associate Engineer, Mr.. VIM. T.
Skunk, as being not only more eco
nomical of material than the usual
form, but as being really stronger
than with the ordinary dimensions /;
the arch is struck from three cehters
and is so designed that The line of
pressure falls within the middle
third of the arch. This is another
evidence of the care and attention
to detail and proper economy in
construction characteristic OF the
present engineering management.
Another new departure was noticed
in the box-drain plans as men
toned, stone of suitable character is
very scarce, and covering stone
proper for use in these drains so diff
ficult to get that their cost is prohib-
itory. But here again Mr.. Skunk
has brought into play his strong
common sense and has utilized a
tough but thin laminated stone
found in the neighborhood /; he has
substituted arches and walls of this
stone laid in full cement for the usu-
al covering stone and heavy side
walls, reasoning that as the Romans
used thin tile and good cement for
some Of their most lasting work this
same construction would do good
service here. 1t is hint worth re-
membering.
In summing up the results of our
trip over the South Pennsylvania
Railroad. we give some general data
picked up by the way. The dis
tance from Harrisburg to Pittsburgh
will be 2l3 miles. The highest ele-
vation attained is at the Laurel Hill
Tunnel, 2,444 feet above tide. The
maximum gradient is 52.8 #. going
west from Harrisburg until the foot
of the Allegheny range is reached at
New Baltimore where the ascent is
made at the rate of So #. per mile
on plane 10 miles in length. The
Allegheny Summit having been
reached, a maximum of 26 40 #.
per mile is used over the undulating
| ground along the divide between
| the Allegheny mountains and Lau-
! rel Hill. The descent of the western
slope of the Laurel Hill required the
use of los #. per mile for a distance
of 6 miles this puts the line fairly
on the crest of the connecting ridge
between the Laurel Hill and the
Chestnut ridge; then to descend
/ from the Chestnut Ridge into the
I water shed of the Sewickly, 105 #.
! per mile is again resorted to for a
distance of 6 miles !; the foot of this