6 SCIENCE. 
Professor William Harkness, who retired 
from active service on December 15, 1899, 
was succeeded in the astronomical director- 
ship by Professor Stimson J. Brown, the 
senior professor of mathematics on duty at 
the Observatory. Professor Brown’s first 
duty was as member of a board of examin- 
ers, to fill the vacancy caused by the retire- 
ment of Professor Harkness, by the selection 
of a suitable candidate for appointment as 
professor of mathematics in the navy. The 
labors of this board, of which Professor 
William Hendrickson, U.S. N., was senior 
member, resulted in the selection and ap- 
pointment of Professor W. S. Hichelberger. 
In this connection it is pertinent to observe 
that the present condition of the astronom- 
ical staff of the Observatory is highly satis- 
factory, and gives promise for the future. 
The vacancies, caused by the rapid succes- 
sive retirement of the older professors, have 
all been filled by young men of marked 
ability, and the Observatory has followed its 
traditional policy in this respect, and has 
every reason to anticipate a renewed ac- 
tivity and a period of harmony, industry 
and usefulness. 
All the astronomical instruments of the 
Observatory have been steadily and contin- 
uously in use during the year on every clear 
night and day. 
The XX VI.-inch equatorial telescope has 
been employed on the observation of diffi- 
cult double stars, the satellites of the plan- 
ets and the measurement of their disks, and 
on other objects suitable to an instrument 
of its power. This instrument was in 
charge of Professor Brown, assisted by Pro- 
fessor T. J. J. See, until December 15th, 
and has since been in charge of Professor 
See. 
In the month of October, during the hazy 
weather common at that season, the images 
of celestial bodies were marked by great 
steadiness in the field of view, unusual at 
other times. Owing to this favorable con- 
[N.S. Vou. XIII. No. 314. 
dition, Professor See noticed on several oc- 
casions faint markings on the disk of Nep- 
tune, similar to the equatorial belts of the 
planets Jupiter andSaturn. The fine defi- 
nition at this time was ascribed to the se- 
lective absorption of the haze caused by the 
smoke of forest fires, and an attempt has 
been made by Professor See and Mr. George 
H. Peters, the photographer, to reproduce 
artificially the same conditions by the use 
of acolor screen. The idea of this applica- 
tion to the telescope was not wholly new, 
although it was believed to be so at the 
time. It is too early to speak definitely on 
the result of these experiments, except to 
say that the general effect of the use of a. 
screen composed of two thin sheets of plate- 
glass, the space between them being filled 
with a solution of chloride of copper and 
picric acid, or a solution of bichromate or 
chromate of potash, seems to have the ef- 
fect of absorbing the blue rays and remov- 
ing the halo which surrounds bright objects 
in the field of a large achromatic telescope, 
and the image appears somewhat steadied. 
The color screen is now in use in observa- 
tions of the diameters of the planets and 
measurable satellites. 
During the year the double floor, which 
was appropriated for last year, designed to 
obviate the difficulty experienced from cur- 
rents of warm air rising from the basement, 
has been finished, and answers every expec- 
tation, giving highly satisfactory results. 
The IX.-inch transit circle was undergo- 
ing its periodical repairs and general over- 
hauling from the beginning of the fiscal 
year until January 20, 1900, during which 
time the routine work of the sun, moon and 
planets was carried on with the new VI.- 
inch steel transit circle. Since the resump- 
tion of the regular work on the IX.-inch 
circle, Professor Skinner has had charge of 
the zone observations and Professor Hichel- 
berger of the routine sun, moon and planet 
work, while the V1.-inch circle, in charge of 
