ON THE TOTAL ECLIPSE OF THE SUN, MAY 28, 1900. 
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Pholographers. 
J. Knight, Sick Berth Steward. B. Bui.brook, A.B. 
Avle-fle-Camp to Sir Norman Lockyer, K.C.B., F.lt.S. 
Mr. C. C. Lambert, Midshipman, P.N. 
the expedition was on board the ‘‘ Thesens” for one day only before the eclipse, 
and as the ship’s parties returned to the ship every evening, it was not possible to 
give instruction in the observation of spectra, and parties for tliis branch of eclipse 
work could not therefore be organised. 
Assistance in Time-heeping. 
Lieutenant Andrews, L.N., who assisted in the important duty of time-keeping, 
has drawn up the following statement of the procedure adopted :— 
“ A time signal was made daily, at noon, from the ship by the Commander ; the 
error of the chronometer having been ascertained by telegraph on the 16th May, 
the day we left Gibraltar. 
“ The deck watch (which was daily compared with the chronometers) was also 
landed, so that I could give any comparison or time required. 
“ On the day of the eclipse I gave the time from the deck watch, 10 minutes before 
totality, on which the ‘ Rise up ’ was sounded on the bugle, and 5 minutes before 
totality, on which the ‘ Alert’ was sounded.” 
The observations of tire cusps to signal intervals of 16 and 5 seconds before totality 
were also made by Lieutenant Andrews, who remarks that the apjraratus provided 
worked most satisfactorily. During the drills, when the cusps were of course not 
observable, the corresponding signals were given by reference to the deck watch. 
The Coronagraphs. 
Three coronagraphs were employed by officers and men of H.M.S. “ Theseus,” 
particulars of which are appended :— 
(1.) The De la Rue coronagraph. Aperture 4f inches, focal length 8 feet. 
Assistant Eno-ineer H. W. Portch in charge. 
O O 
The instrument, which had previously been used in Nova Zemlya and India, was 
fed by a spare part of the ccelostat mirror used for the long-focus coronagraph. Three 
exposures were made of approximate durations, 40 seconds, 15 seconds, and 0-5 second 
respectively, the plates employed being “ Sanded ” triple coated, 6 inches square. 
(2.) The Dalhneyer coronagraph. Aperture 6 inches, focal length 54 inches. 
Surgeon J. Martin in charge. 
