The Placer herald., 1860-03-31

reduced TO a seven degree curve. (radluS SlJ lect
by Il moderate additional cost. The whole length
of road is l00.756 feet or 1908 miles.
OF this there are
OF straight lines 39 622 IT, 80 miles or 1913 per ct
OF 10 rad. $3.50 it. 700 Ut. or 0.l3 ms. o. "
Of2o cur rad. 1865 IT. 2200 IT. or o.il ms. or 80"
OF 80 rad 1910 IT, l3400 it. or 2.5l ms. or 1872
OF 40 rad. 1893 .l4l #. or 269 ms. or al
OF so rad. lllG tl2,350ft. or 2.34 ms. or l23
OfGo rad. 1854 IT, 200 it. or PIP ms. or Ill
OF 10 cur. rad $40 #. $500 It. looms. or 6.3"
or cur. rad. 7l6.S IT, 500 f. or OILS ms. or 0S"
If the lower line is adopted there will be 900
feet more of 50 curve, 500 feet of nine degrees,
(or G37 3 feet radius) and six curves making to-
gcthcr $500 feet Of ten degree curvcs-or 513.7
feet radus.)
The tendency of sharp curvature on II road is to
increase the resistance to the trains, and the ric
tion and wear and tear of rails and machinery.
The evil does not end with the construction of
the road but is perpetuated in its daily use. The
same remark therefore is applicable TO this rs to
the steep grade that no feature should be admit
ted in the location which would unfit the road for
the purposes OF Il main trunk road aero $ the
Sierra. For this reason | would much prefer to
limit the curvature to seven degrees: especially
if it should be ascertuined that this curvature
may be adopted as q maximum on the extension
of the road to Nevada.
Trestle Bridges.
The most formidable item OF cost is that of the
high trestework necessary Tor passing the deep
ravincs known l}anvnrd ravne, Baltimore ra-
vine, and Dutch rayne. They are common to
both the upper and lower lines being of course
both higher and longer on the upper line. had
at first designed that the hi CHER portions Of these
bridges should be of arch and lattice truss. ON
Halls plan, sustained by piers either of wood or
masonry 1t was found that piers of masonry
would be too costly. And although something
might at first be saved by the truss, with wooden
piers, yet there appeared to be an advantage in
using lrcstework, even at II slightly greater cost
on the high trestes because in case of a partial
decay OF tmberS. one can be removed and another
replaced without disturbing the whole structure.
There being no large flow of water to interfere
with the foundation, a truss bridge not ncces-
sary on that account. At Banvards ravinc on
the upper line the bridge is 1900 feet loag, l35
feet high at the stream. and diminishing in height
towards each end to 80 and 25 feet At Bnlti-
more ravine the bridge is 900 feet long, and 100
feet high ut the stream The bridge ut Dutch
ravinc is 500 feet long and rs feet high in the
centre,
On the lower line the bridge at Banvard ra-
vine is 600 feet long and ~ feet above the stream;
at Baltimore ravinc $40 feet long, and LOG feet
above the stream; at Little Baltimore ravinc 420
feet long and 81 feet above the stream, and at
Dutch ravnc 200 feet long and 81 feet above the
stream.
Every effort was made by repeated trial lines
ut different points to avoid these high crossings;
but any line that diminished the height Of the
bridging ran into rock cutting of impracticable
depth. or at best too costly for adoption. For
the upper line two different locations were sakcd
out across Banvard and Baltimore lines, One
designated as 1.-THE middle line represented on
the map by the continuous red line. and another
signatcd as 1.-THE air line marked on the map
by II dotted line. The main profile is adapted to
the middle line, and shows small cut through
the intervening ridge between the two ravincs-
J1,r,, ion I.,,I ,vit Ii,n IN
the map. this cut light be avoided, by crossing
the low ridge at its surface and possibly without
IA very great increase in the hcig of the bridge.
On the air line it is proposed TO make one long
bridge OF trestlewolk covering me entire chasm
of both rnvincs and passing over the intermedi-
ate ridge about thirty feet above it. BY this
line, as it is lower down the stream, the extreme
height is increased at Baltimore ravine TO $50
feet at Bunvnrd ruvnc to 1913 feet but the cost
of trcstlework and masonry together is S571 less
on the nir line than on the middle line. There
are nine more trcstcs on the air line, but the in
crease in number is over the low ridge, and there
are less of the higher class of trestlcs. lstima-
ting masonry, cmbankment and trcstlcwork to-
gethcr, for the entire crossing of both rAvincs
shows the air line the cheapest by about $ 1900
This line increases the height, but gives much
better working line by reason Of its straghtncss;
II merit of no small Importance in crossing high
bridges.
sing bridges Of this height, but the danger of ac-
cidcnt is about the same on II bridge Of 100 feet
high as ON one Of lSO.Nor are such hegh without
precedent. The Genesec High. Bridge. over Gen
esce river, near Portagevile, on the Buffalo and
New Y ork railroad, built by II. g. Seymour, is
800 feet long, and $50 feet above the river. 1t
has eight stone piers 30 feet high, upon which
are plat ed trcstes 1870 feet high, sevcnty-iive
feet wide at base, and twenty-five at top. Upon
the top of all is placed bridge fourteen feet
high The structure contanc one and u half
millions of feet of lumber. board measure.
The plan for the timber work Of the trcstlcs on
this road is the s"nc as that of the trcstlesat the
Folsom road bridge, except that we propose
to add bolster Of feet long, II inches ~ II
inches, boted to the stringer by four bolts on one
inch iron. The tresles are designed to be 20
feet apart from centre to centre lengthwisr OF the
road, connected by stringers for the track. II
inches by Is inches Between every two trcstlcs
long gitudnuly, the stringcrs are sustained in the
centre by diagonal braces mortised into the posts.
The track is sustained by two vertical posts II
inches by II inches, one under each rail. These
vertical posts are braccd latcrally by long ding
ona braces 10 inches by II inches, inclined at an
angle of 10 l5' and stepped into the same ground
sill as the vertical posts. These posts and braces
are siflencd by cross-ties at intervals vertically
of ten feet, these ties being boltcd to the posts
and main braces The trestles are tied to each
other longitudnally by ties notched and spiked
to the posts and braces ut vertical intervals of 10
feet A cap 10 feet long, II inches by II inches,
ties the two vertical posts at top tranSversly, and
suStains the holsters which are bolted to it, The
size of the vertical posts is increased the height
increases, the lower posts being either II inches
by IA inches, or double posts OF 10 by 2 each, in
place Of each single one. At heights over 60
feet an extra set Of vertical posts and lateral
braces is introduced, and another set at over l20
feet.
The length of sill increases with the height;
that of trestlc 80 feet high, being 2S feet long,
and for $50 feet high 1873 feet long
The more important; timbers OF the trestles,
such as the sills posts main braces, caps, holsters
and stringers. ought to be either of Redwood or
of Puget Sound Pine. 1t would be better if the
whole would be of the same quality Perhaps,