138 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
ask for the loan of these instruments. As Father Cortie found it 
impossible to spare the necessary time for the expedition his place 
was taken by Doctor Crommelin of the Royal Observatory. 
8. In Novefiaber, 1918, the only workman available at the Royal 
Observatory was the mechanic, the carpenter not having been re- 
leased from military service. In these circumstances Mr. Bowen, 
the civil engineer at the Royal Naval College, was consulted. He 
kindly undertook the construction of frame huts covered with canvas, 
which could be easily packed and readily put together. These were 
generally similar to those used in previous expeditions from the Royal 
Observatory. (See Monthly Notices, \ol. LVII., p. 101.) He also 
lent the services of a joiner who worked at the observatoiy on the 
woodwork of the instruments. 
It was found possible to obtain steel tubes for the astrographic ob- 
jectives. These were, for convenience of carriage, made in two sec- 
tions which could be bolted together. The tubes were provided with 
flanges at each end, the objective being attached to one of these, and 
a wooden breech piece to the other. In the breech piece suitable pro- 
vision was made for the focusing and squaring on of the plates. The 
plate holders were of a simple construction, permitting the plate to 
be pushed into contact with three metal tilting screws on the breech 
piece thus insuring a constancy of focal plane. Eighteen plate-car- 
riers were obtained for each of the astrographic telescopes, made 
according to a pattern supplied. 
With the 4-inch lens Father Cortie lent the square wooden tube used 
by him in 1914. This was modified at the breech end to secure greater 
rigidity and constancy of focus. 
It was designed for dark slides carrying 10 by 8-inch plates, and 
four of these, carrying eight plates, were lent with the telescope. The 
desirability of using larger plates was considered, but the time at 
disposal to make the necessary alterations was insufficient. 
The 16-inch coelostats which had been overhauled by Mr. Cotting- 
ham were mounted and tested as far as the unfavorable weather con- 
ditions of February, 1919, would permit. The 8-inch coelostat was 
constructed for these latitudes. To make it serviceable near the equa- 
tor a strong wooden wedge was made on which the coelostat was 
bolted. 
The 8-inch mirror was silvered at the observatory, but owing to 
lack of facilities for maintaining a uniform temperature approach- 
ing 60° F. in the wintry Aveather of February, the larger mirrors were 
sent away to be silvered. 
Photographic plates, suitably packed in hermetically sealed tin 
boxes, were obtained from the Ilford and Imperial Cos, The liford 
