The morning times., 1896-12-25

moSo oae, and is so arranged that points
similar to those made ordinarily every
five minutes, Will be traced upon the re-
curling paper by the fountain pen ivory
time the point OF the needle in the seis-
moss ope touches against the rim of the
platnuU-lned hcle mentioned above.
Thus The acton or me earthquake is
shown by single point or a series Of
points falling between those regularly made.
The exact inst ance Of the disturbance may
he determined by cutting off the number
OF five minute marks made since a known
.ime, noted when the record WAS begun,
and by applying a carefully graduated
scale, which Will show how many minutes,
/ seconds ana fractions thereof the instant
.he shock exceeded the last fivc-niinute
mark preceding.
The other apparatus for recording
the presence ana ACTON al earthquakes tnaU
may visit Washington is placed In "A tall,
dark chamber in the Washington Monument.
Ii Is hardly correct TO call 1t a SeiSnoscope,
for II is not intended primarily for the OBJ
servation OF earthquakes. It's purpose is
10 determine any variation from the plumb
VI the great structure of which it is a
part. But as SeSmoscope IL is the big
gest in the world, and its working is prob
ably dis satisfactory as that OF the nicChan-
isns especially designed for the study under
discussion.
The essential features are the tremen-
dous immovable mass of the monument IT.
self, which can hardly be affected by any
trembling of the earth less deep than an
earthquake and long copper wire to
which plumet is suspended, making
probably the longest pendulum in the
world. With a base which is inSenIble
to any ordinary disturbances in the To-
cality, even to the firing of large cannon,
and a pendulum that will vibrate upon
the slightest motion OF the monument,
there is u certainty that anything i'll the
nature Of an upheaval of the entire surface
OF the earth, no matter how slight, will
be noted by the great pendulum, ana that
nothing else will There are, however,
two other tremendous though usurlly 1T
| tie noticed forces, whose effect upon the
monument are recorded by the mechanism.
( These are the wind and sun
The plumet that hangs in the dark cam
! ber is let fall into a vessel of oil. The
other end of the Wire is attached at the
center of gravity Of the monument 81 feet
from the ground-Or, to be more accurate,
from the end OF the mass Of metal that cor
responds to the ball OF the pendulum.
Daily observations.
At the lower end just above the pIumuet
are focused two transit instruments, ard
by their aid the custodian OF the tower
takes an observation every day and at the
War Department. If the monument leans
the fraction of an inch at any If these OBJ
servationS tits shown on "A finely graduated
scale that forms part of the transit.
But there Is no self acting apparatus TO
keep record of dstuTba nces that may af-
feet the great pendulum; 50 the Usefulness OF
/ the apparatus rs means of observing
earthquakes is lost.
Special observations have shown that the
force Of n strong wind changes the line Of
the great structure from a vertical and
after the hurricane of September 20 the
observation revealed the fact that the
plumb line had been detected from the nor
NAL position, but it was only one fifteenth of
an inch. IL may be, however, that the
movement was greater when Z he storm Was
at the height Of its fury. Gen. Casey, who
5uperinteEded the completion of the monu-
rnent, calculated that no wind blowing al a
rate less than 100 miles an hour. could
| cause the least danger, and an army en-
gineer is SAID To have remarked that in his
opinion nothing less than an earthquake
need be feared. The wire has been noticed
40 bc drawn one side or the other by other
high winds, but the conmonest cause if its
DETECTION is the heat Of the sun
in midsummer. This lifts the mighty
oselisk from its plumb regularly every
very hot day. The explanation is that
the heat expands the south face of the
Monument very much more than il does
the other sides. In consequence the top
is tipped slightly 20 the north. The OBJ
served facts correspond with this; for the
plumb line moves toward the north in
the middle of the hot days.
Owing to the lack Of an automatic in
strument to record variations OF the Wire
from the plumb, the earthquake shocks
felt here a year ago left no data at the
monument. 1t is probable some day this
addition will be made, and the results OBJ
tanned viii be turned over to the students
of earthquakes.
Earthquakes Booked.
At the Weather Bureau the shocks of n
year ago, although very light, We're faith
fully noted by the seismugraph. 1t oc-
CURED on September l , and was felt by
very few persons in this city, hut made it
self plainly known in Philadelphia and that
vicinity. 1t was not till two days after
ward that anyone looked to see whether
the instrument had made any note of the
shock. 1t was found that it had set down
6 hours 8 minutes and 80 seconds H. n.
| as the exact time the trembling was felt
here. Soon after a second shock occurred
| along the Atlantic and was not felt here
| at all. Its presence was officially recorded
| by the mechanism at the Weather Bureau.
The great September storm OF tiis
year also made a mark on the Weather
| Bureau cylinder for earthquakes, but it is
not DelleNeu on UnaU account tflat lie
| storm was accompanied by an earthquake.
| The bureau officials think the vibration
! was caused by the fact that tn wind prob
| ably shook the entire bureau building, in
| Guiding the solid base of cement of the
! seismoscope.
There are two or three regions in the
| United States well adapted to the study
| of earthquakes. One Of these is the Cali.
| fornia region, where such trembings of
| the earth are not infrcquent and little ar
| tentioD is paid to them by the public
| Another Is in the center of the Mississippi
| Valley, in the section where the Ohio
| River empties into the Mississippi. There
| fifty years ago a tremendous conVuiSion
| occurred, and "a. considerable stretch Of
| ground slid down a distance of thirty
| feet below the level of the surrounding
| country. 1t is generally believed in that
| part of the country that this earthquake,
| which is named from the nearest town
New Madrid. Mo. was in some wav cans