DETERMINATION OF DEFLECTION OF LIGHT BY THE SLTN’R GRAVITATIONAL FIELD. 21)5 
by Prof. Bauer, who was there on an expedition to observe magnetic effects. At the 
station at Panganyika it was thought tlie sun was at too low an altitude for observations 
of this character, owing to the large displacements which would be caused by refraction. 
A circular received from Dr. Morize, the director of the Observatory at Kio, stated 
that Sobral was the most suitable station in North Brazil and gave copious information 
of the meteorological conditions, mode of access, &c. 
7. Acting on tliis information the Joint Permanent Eclipse Committee at a meeting 
on November 10, 1917, decided, if possible, to send expeditions to Sobral in North 
Brazil, and to the island of Principe. Application was made to the Government Grant 
Committee for £100 for instruments and £1,000 for the expedition, and a sub-committee 
consisting of Sir F. W. Dyson, Prof. Eddington, Prof. Fowler and Prof. Turner 
was appointed to make arrangements for the expeditions. Tliis sub-committee met in 
May and June, 1918, and made provisional arrangements for Prof. Eddington and 
Mr. CoTTiNGHAM to take the object glass of the Oxford astrographic telescope to 
Principe, and hD. Davidson and Father Cortie to take the object glass of the Greenwich 
astrographic telescope to Sobral. It was arranged for the clocks and mechanism of the 
coelostats to be overhauled by Mr. Cottingham. Preliminary inquiries were also set 
on foot as to shipping facilities, from which it appeared very doubtful whether the 
expeditions could be carried through. 
Conditions had changed materially in November, 1918, and at a meeting of the sub¬ 
committee on November 8, it was arranged to assemble the instruments at Greenwich, 
and make necessary arrangements with all speed for the observers to leave England by 
the end of February, 1919. In addition to the astrograpliic object glasses fed by 16-inch 
coelostats. Father Cortie suggested to the sub-committee the use of the 4-inch telescope 
of 19-feet focus, which he had used at Hernosand, Sweden, in 1914, in conjunction with 
an 8-inch ccelostat, the property of the Eoyal Irish Academy. It was arranged to 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 Dr. Crommelin of the Royal 
Observatory. 
8. In November, 1918, the only workman available at the Royal Observatory was the 
mechanic, the carpenter not having been released from military service. In these 
circumstances Mi-. 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,’ Vol. EVIL, 
p. 101). He also lent the services of a joiner who worked at the Observatory on the 
woodwork of the instruments. 
It was found possible to obtain steel tubes for the astrographic objectives. These 
were, for convenience of carriage, made in two sections 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 provision 
