Evening star., 1898-12-14
Interesting Facts Regarding the
Washington Monument.
WHAT Is DISCLOSED BY A PLUMMET
Proposed Method of Obtaining a
Continuous Record.
LOCATING THE SHAFT

He has made as thorough a study of the
physical conduct of the monument as the
limited facilities at his disposal would per-
init, and has embodied the results in an
official report to the chief of engineers
He finds generally that the top of the
monument moves about three times as far
as the center of gravity; that the monu-
ment rises and falls, and also incliues first
in one direction and then in another but
that these movements do not affect its
stability.
The following official data relative to the
monument will undoubtedly contribute to
a better understanding of the technical
statements made in the report:
Height above mean low water, J97 feet
" inches. height above doorsill, 900 feet
Side of base, outside, ID feet 112 inches; IN
side. % feet. Foundation depth (sand and
claD, 80 feet; foundation size. at bottom
on a side, 1851 feet; founda ton area,
III, o02 % square feet Top side of monument
outside, 81 feet inches; inside, 81 feet &
inches. Walls, thickness, base, IL feet a
inch top, is inches. Weight of capstone
5000 pounds; weight of whole monument,
81 ,120 tons. Mean pressure of monument
at base, . tons per square foot. Pressure
on foundation, nowhere greater than 9
tons per square foot; near edges, less than
3 tons. Coast survey report, December /.
lsS1) Taper of monument, 4 inch to l
81
feet, ending at $50 feet, 10 Steps sos:
landings %. Windows. at top only, ) feet
by 1l3 inches. six; 8 feet by . inches (east
side,, two. fine TO ascend in elevator, 9
minutes; time to descend in elevator 8
minutes. Elevator, tested to 10 tons: load
allowed, persons, 10: cables diameter 10
inches. Cost, $1,3O0000. Corner stone laid
July 4, 1S4S. Capstone set December 6,
1881. Dedicated February u, 1850.
June l.. 1887. a plummet line was set in
[ dot lail and
sometimes hourly readings have been taken
whenever the conditions would permit
From that time the daily plumb records are
complete, save in the few instances about
10o in all, when readings Were impossible
because of the swayng or vibration of the
Wire. The records are very complete so
far as they go, giving daily readings from
the north and east instruments, and the
daily variation from zero, north. south.
east and west as the case may be- The
readings are interesting from a scientific
STANDPOINT, but are too technical and vo!u-
mlnous for newspaper reproduction. The
report, i'll part is as follows:
The PIummet.
The plummet consists of a copper wire
3-64-inch in diameter suspended from the
horizontal plane containing the center of
gravity of the monument, which is at a
height of III feet 10la inches above the
door sill of the monument
The top of the wire is attached to an ad-
Unstable brass screw fastened into the m
derside of north and south I-beam at a
point about ten feet from the west wall
of the monument
At the bottom the wire is attached to
another adjustable screw fastened to a
twenty y-five-pound brass plumb bob The
bob is suspended in a bucket Of water
to prevent movement from ordinary vibra-
ton.
The wire itself is protected from top to
bottom by casing of galvanized iron pipe
fastened at top to the underside of the l.
beam above referred to, and secured to the
braces of the stairway by cir
cular bands Of iron. Near the floor this
pipe expands into a hood and is connected
to the plummet house (Which Is also of
galvanized from by riveting and soldering
In the interior Of the Dlummet house is
a hollow iron pedestal bolted to the floor
with a pinch circular opening on TOP for
the free passage of the plumb wire. on the
east side of the pedestal is q door which
gives access to the interior, in which stands
the bucket OF water containing the plumb
bob.
On top OF the pedestal are two telescopes
one on the north side facing south and one
on the east side facing west. These tcle-
scopes are moved by micrometer screws
which cause them to travel, the north one
along an east and west graduated scale
the east one along north and south grad
uated scale The readings of the north in
Strument increase to the west; of the east
to the south.
The scales are graduated to inches and
twenteths of an inch, and by means of
micrometer graduated into 30 sections 70
threads to l inch) may be read TO thous-
andths Of an inch.
Reading of the Scales.
Variations in the positions of the plum
met line are determined by variations in
the readings of the scales when the plum
met line comedies with the center vertical
wires of both telescopes. In letter to
Col. ]. NJ. Wilson, Corps of Engineers,
dated April Z, 1888. and written by Mr..
G. M Thomas, clerk. is said: The plum
met was set to a point on the floor of the
monument on the 18th of June. 1887, with
the following as the result of the read
ing: o.926" north dnstrumenD; o"795" east
Qnstrument'
From a letter to the chief of engineers,
United States Army, from Col. o. II. Ernst,
Corps of Engineers, dated February II,
1891, it appears that in 1SSS the maximum
movement was 015"; in 1889, 0i6"; in 1880,
u. ~.
was one-tenth of an inch W10) southeast
of where ii was January g. 1SSS
The extreme positions of the center of
gravity during the three years 1883 1889,
and in the other August ., 1890, the dis
eance between these two positions being
one-fourth of an inch m.25").
The record for June 20, 1898, is as follows:
North instrument, 0.93S inches: east instru-
ment. 09G0 inches variations from zero
north, Obs; west, .012. To show the vara
tions during short periods ii is stated that
on June 4, 1898, the reading was as follows:
North instrument .S96; east instrument.
.944; variation from Zero-north, 1855;
east .O30.
The top of the monument moves about
three times as far the center of gravity.
Owing to the unique character of this
structure many inquiries are received ask
ing for information of various kinds regard
ing ii. Most of these inquiries could be an
swered by sending copies of the level and
piummet records. AS these records will un-
doubtedly become of greater interest as
years go by they have been collated and are
forwarded herewith in order that they may
not be lost and may be available for study.
These records, as will be seen, are quite
rough and not of scientific accuracy. This
fact has led to the following project:
A Continuous Record.
In order to know what Is taking place in
the monument the record of the plummet
should be continuous. 1t is of little value TO
know what these readings are at the same
hour of each day except as a gauge of sta
bilty). But If the travel of the plummet