The Washington times., 1894-11-11
MERCURY CROSSED The sun
Transit of the Planet Photographed at
the Naval Observatory.
131 NEGATIVES WE'RE SECURED
It Was Splendid Day for Observation and
the Astronomical Staff Did Some Valuable
Scientific Work-Mrs. Cleveland Took a
Look Through the Big telescope.

Sunshine and weather combined to make
servation of the transit of Mercury. bril-
liant sun blazed out of a clear blue sky that
was only fiecked here and there with light,
fieecy clouds. and the atmosphere was as
lucid as a crystal. Toward sunset, however,
long bank OF dark blue clouds drifted up
ward from the horizon and obscured the final
contacts of the little planet with the suns
disc.
The members OF the astronomical staff of
the Naval Observatory made the best of their
fine opportunity to observe the transit. Late
Friday night the finishing touches we're
given to the photoheliograph, and early yes
terday morning every possible preparation
known to modern astronomical science had
been made for the valuable observations
which were recorded yesterday. Months will
elapse before these observations are made
known TO the scientific world. and the major
ity of people will never even hear Of them.
According to the computation of the Naval
Observatory Mercury was two minutes be-
hind in his time schedule. and the first con-
tact occurred two minutes later than expected,
or at l1h sim 45s instead of 11h 45m 45s, as
computed. In other words the Naval OBJ
seryatory astronomers had located the planet
two minutes farther along in his orbit than
he really was. The source of this error is
at present unknown, but Prof. Harkness
| believes Mercury is responsible for misleading
| the astronomical mathematicians.
Observations were made through six sep
aIate instruments. Prof. Brown presided at
| the great equatorial, which has 26-inch
| lens. and Prof Frisby at the 9-inch equa-
| torial. Profs. Newcomb and Eastman also
made observations. The other instruments
used were three 5-inch telescopes and the
| transit instrument, the latter In connection
| with the photoheliograph.
The most important work Of the day was
| done by the photoheliograph. which was in
| charge Of Messrs. G. A. Hill. Charles T. Fel-
| lows. William Brown. E. A. Boeger, OF the
observatory staff, and William F. Cullen. a
! local photographer unconnected with the OBJ
serYatory. A photoheliograph Is a photo
graphic camera especially arranged for taking
negatives Of the sun. In this instrument the
suns image is reflected by glass mirror
through forty-foot tube upon a sensitive
plate. The wet process Is used but exposure
is instantaneous.
Yesterdays work with the photohelograph
was extremely satisfactory. Light clouds IN
/ tsrfered with its operations somewhat, and
! the trees in the Observatory grounds pre-
vented altogether the taking Of negatives after
! 1854 O'Clock, but the operators were kept busy
from 10 o'clock in the morning until after
o'clock in the afternoon with fattering re-
suits. The first negative was exposed at 11:11
a. m, and between that time and 1854 .. m
when the last exposure was made, 131 mega
tives were taken.
These negatives show the suns circular
/ image as dark shadow on a square plate o
glass. Mercury appearing as small clear dot
less than the size OF a pinhead. and appa
rehtly indistinguishable from a number o.
similar dots also appearing on the plate, rep.
resenting the spots on the sun. For months
to come the attaches of the Naval Observatory
will use these plates for the purpose of secur
ing by measurements the exact position o
Mercury at various times during the transit
BY means OF chronograph the exact time o
each exposure is automatically registered. and
so q perfect record of the time at which thu
/ planet reaches the point shown in the mega
| tive is obtained.
Among the visitors during the day were
! Mrs. Cleveland and her friend Miss Willard
of Baltimore, weo came about noon and tool
look at the transit through the 9-inch equa
toriaI Mrs. Cleveland was very much de
lighted with her astronomical diversion
Other visitors during the afternoon were th'
Secretary of the Navy and Mrs. Benjamin
NIicou, the Secretary of State and Mrs
Gresham, and Mrs. Lamont. Capt. T. "
McNair and Prof. Harkness received thes
guests and escorted them about the build
ings and grounds.