The Seattle post-intelligencer. [volume] (Seattle, Wash. Terr. [Wash.]) 1888-1914, 1890-06-30

an. ~ % I'm assumed ct the beginning of the
S4lsey are not uncommon waan an adj
netence 70 II would lead to heavier work
~. 'a1ser desours than are deemed advisa-
The duty Of the topoeranher il 70 asce,.
tam ct what rate the slopes rise or fall on
eacu SIDE OF the traverse. to take full notes
- .uc Watercouraes, 10 record the artificial
IeA.ures OF the country, such as houses.
aoaus, FENCES, etc, and in general TO gather
every KIND OF Information which may help
T ~ ae s ne most advantageous location
lie heio appliances are a hand Level and
cnAin or slope rule, which gives Inc angle
. py the surface of the grounp with
TIE horizontal. Where stadia survevfnv IL
empioyed, however, the functions Of the
iese1ef ana the topographer are to a very
sieas extent combined with those of the
arh h.ah he observes the vertical angle
the roo Is held and his instrument makes
WIN .ne horizontal, and as he already
Aaows the distance, according to the
me nod explained above, he is able BY
simple trlSoromecal calculation 10 esti-
mate TIE difference of elevation between
nis instrument and the point observed.
Dut IN whatever way this Typographical
information may have been OBTAINED. thu
pest way to utilize it is undoubtedly TO plot
II Dy contour lines, that ia. the lines of
equivalent height, which may be imagined
70 run round the slopes at certain liked
eeyations, usually five or ten five apart. A
suineient number of points are observed to
H Hnaoie me draugntsman to lay down these
lnes on the map so as to show their inter-
sections with and courses on each side of
the traverse. The curved lines of the dia-
gram skeiched above indicate the contours
oil the surface. The vertical distance be-
tween them Is always a fixed number OF
Ieet fof any particular map, so that to find
Ine rate OF ssope at any spot on the ground
one would have merely to apply a scale to
the map and read off the horizontal dis
lance between the.tw consecutive lines.
Nhen the preliminary surveys have been
completed It remains 10 establish the best
location of the road from the information
which has been accumulated. With the
maps before him the engineer is now not
only able 70 take bird s-eye view of the
country, but also TO estimate very CLOSELY
what profile would be presented by the
grade II the line were thrown into some
particular position. He can thus fix upon
the most desirable location for the road
with great rapidity and precision. Ere
quentiy he can solve some knotty problem
py Anew hours OF office work more satisfac-
toriiy than large survey party. if it were
occupied for the same number of weeks in
running experimental lines on the ground
itself.
The line is staked out in the field from
notes taken down as the paper location ad-
vances. This process will, of course, dis
close some errors and imperfections, lust
as the enlargement OF photograph reveals
many blemishes which had before escaped
notice: but If the field work and map of
the preliminary survey have received
proper care few serious changes will be
found necessary.
As every one knows, q railroad line is
hAp a
portions are termed tangents. because they
must touch the curves. in order that the
passage of the cars from one to the other
may be as easy as possible. This rigid con-
dillon OF tangency makes locality q much
more difficult task than 1t would be if some
freedom were allowed in the mannor of
connecting the two, and gives rise to a
number OF interesting mathematical prob
lens. Another rule which is often trouble
some is that two curves bending in oppo-
site directions must not follow one another
without the Intervention of a piece of
straight track, aDout 100 feet being the
shortest distance ever admitted in the
toughest country. The curves are in Eng
land always described as of so many feet
radius. but in this country as being of so
many degrees. For example, if a one
degree curve is spoken of, it means that
every one hundred feet of the curve ex-
tends over one Observation-Disclosures tieths
part OF the circle to which il belongs. On
the other hand, after 900 feet OF q ten
degree curve have been measured, one will
again have reached the starting point The
reason why reference is made in this nom-
euclature 10 one hundred feet is that engi-
neers have adopted a chain of that length
instead of the old Gunter's chain of sixty.
six feet. But in whatever manner curve
may be described, it Is in all countries
traced on the ground by means of a transit
or other angie-measuring instrument.
The stalking out OF the line is the last of
the operations which are comprehended in
the term location. Enough has been said
to give the reader some notion Of the many
complex problems which an engineer has
to solve before a shovelfu of earth has been
cast and to indicate the extent of the out
lay upon work which merely leads up to
the construction of the road. Skill and ex-
perience may not only produce better re-
suits, but greatly shorten the process of
locating the line, but no amount of ability
can obviate the necessity of q patient and
exhaustive investigation of all the possibili-
ties OF the country 10 be traversed Many
q company has been driven to bankruptcy
simply because in its haste to begin con-
struction, or out of false ideas of economy,
it has not devoted sufficient time and
money to the discovery of the best position
for the grade That there is no royal road
TO location is q truth too often forgotten or
ignored until bitter experience has lent it
point and emphasis.