The Seattle post-intelligencer. [volume] (Seattle, Wash. Terr. [Wash.]) 1888-1914, 1892-12-21
st Of tho work win BE- done alrect,v !,

'a.ssy; .s,,:, ....,,.,., = : s.1s s.ls''l' IS.
a1n oi several prime points. an elaborate
- slapnic trinngnla.fon is used on q pia'
49, 49,. 2. specially mounted paper for thsid-
...s ...a "a the fieid of every object whose exi
.a.,0 sn y required, every object being sight
-1k'sa 10 from different points, and
cneckeo, until nearly absolute accuracy
.aineo vertical angles are carefully me
% teieseopic aiidade. The mapping Jaw.
one the planesabie. tho map being draw
nn1kh in pencil IN the field
| ne plaaetable Is one of the first sur.
InstEuments ever used by man. and OF LAT 'ion
= mas osen greatly elaborated and brougtth
very nigh degree of precision by the en-.
oi the geological survey. 1t is an adjr
Doafu mounted On . tripod aad upon
iastened the paper on which the mapi
aiaWn. This drawing shee. is made d. +
pieces OF paper with a sheet of linen be cItv
1ns pieces Oh paper are mounted on thesen-
win their grains q. right angles, the obi h;.
ing TO prevent any expansion or contract ~ us
sccouat OF moisture Ia the atmosphere -"
On Ihis sheet are accurately laid o. ie"
parallels OF latitude and the meridiaus offs at
.uae, and certain initial points are then rand
~ .nelr exact geographic position witns of
shce 10 Latitude and longitude The alieirr.
-
Heic viewed through the telescope TIL
stfument Is very fine steel ruler with fehs
s.ope mounted upon it. The telescope ID up
DIE OF being pointed up or down 50 as to ntal
u1e vertical angles By means of the aght,
vafious objects are viewed in the field aasfic
ufa"n on the paper to correspond. As obie.
sishteo from yarioas stations the intersect
Two or more lines of sigh. 20 every object
mines Its position on the map. When an sno
.s Is tnus sighted the vertical angle is also
TN THIS and the distance measurement
aihtude OF the objects can be computed.
elevatlons are we'll checked amongst them
ana are based on and further verified by ana
tioas measured by an instrument called u.
level sen-
IN this way the entire field 10 gone ovethe
every house. road. canal. water course, ratthe
In fact every feature of the landscape e
timosr is carefully noted for location and
tude The number of different observatio oiio "
this KIND depends upon the general relief e'eu
country. The relief of the couatry is shogri-
contours or lines of equal elevation. Ii
iying lands or even plains these vary froma to
hse feet elevation TO every twenty-five fe of
rough, mountainous country, from every aars
70 every 100 feet elevation. After ascertaas
as many points as possible where these ST CA
sive attitudes strike, all the points of the
Altitude are connected by lines aeeordingt OF
general confguration of the surface, eithSthe
snort abrupt lines Or by large or tied
curves All this work is done by the eng
In the field. while the landscape is before "a
IN this city she work combines all the -.
ioree OF field sketching with the accuracy 'io
tanned by the most careful surveying OF
IeatEre deaiuested. These lines conuec.ires-
points OF the same altitude are termed col to
Ines, as each line wouid mark the contolnIi-
the shore If the sea should rise to the eiev or,
indicated by it. 2.
IN the process of mapping. all iiues of -
ios determining positions are drawn with"i
greatest fineness. the pencils used being cir
nara and ground TO chisei points. 30 thsng
line hugs closely the steel ruler shat formsur-
ioos OF the alidade All located poiIitson
marked by fine needle punctures, and whel All
observations for any set of located points ;,h
al been repeatedly verified, the sketchin :,
and around these points is carried forwarS'"
the ground 10 occupied, and gradually the me
proceeds step by step until every foot of tn he
tire area of fifteen minutes square has rm
travsrsed, measured. surveyed and care5n-
mapped
"ihe length of time which will be req nirs, :,
do this work depends altogether upon cirs :.
stances This map viii be OF the greatest rit
ness done by the department, to be publihe
on scale of one mile TO an inch, al.hougplti
field scale Will be slightly larger The con
lines will &c at successive elevations OF twent
five feet. The difficulties of work in this raho
are much greater than in many other sect =
owing to the dense timber growth. So gre
this difference that the government. aiiow!!iu
TO eng!nse for running lines in the pr In
land surveys is about ten times as great al inng
plains country. The conditions of weatherye
obstacles to travel and the extent OF the fielte
vision all Influence the length of time reo1, -
to perform the work. -
"a large use OF these maps Is purely ed Va
tionai, being ID request by many of the coifio
and technical societies. and they I'll an iufn-
tant place AZ contributions to abstract seie to
Their great value, however, is not only Tor nv
ernment use In considering the movamen-e
troops in times of war, aud in the study of :.
cation reservoir sites, watershed areas. etc
also Tor a vast number OF economic uses
yond calculation. The building of canals, IN
ways, frrigsting and drainage bitches, he
location of dams, tunnels, aqueducts, brita-
ana roads can all be studied from these man,r
a large extent, even without personal insha
tion OF the field. The stcepuess and heigh.-
slopes or cliffs, the direction of the same,
fall OF water courses, the grades of roads,
are ell graphically illustrated. For legisaas
and all public officials down to road overseal
who have to deal with the phases OF econoad
problems affecting the public. as welisd
for all engiucers aud men OF enterprise IT,,
maps will prove invaluable aids in the PROSE
ton OF their work. From one of these Inapso
accurate profile OF the region mapped can bel
tanned between any two points in any direcsfo
The general publication of these maps is ME
ter OF 90 great public convenience that il is az
prising that such a store of geographic insorsv
ton gathered at so great expense should
buried within the department. vaults at va
ington City" ,