Total Eclipse of the Sun as observed at Ovar, Portugal. 395 



and provided with a light canvas cover when not in use. The equa- 

 torial with the double tube for the small-scale photographs of the 

 corona was covered with a sheet of waterproof canvas when not in use. 

 The arrangement of the different huts and instruments is shown in the 

 accompanying plan. 



The instruments were all erected on May 19, the observers thus 

 having a clear week to adjust them, and to rehearse the observations. 



Personnel. The following list gives the names of those who took 

 part in the observations : 



W. H. M. Christie : Thompson coronagraph. Large scale photo- 

 graphs of corona. 



F. W. Dyson : Double photographic spectroscope. Spectrum of 

 " flash " and of corona. 



C. Davidson : Double camera. Small scale photographs of corona 

 to show extension. 



J. J. Atkinson : Assisted Mr. Dyson, moving plate-holders and 

 changing plates for the flint prism spectroscope. 



A. Berry : Counted seconds for first half of totality, and then set 

 the heliostat for second contact. 



Mrs. Kennedy : Counted seconds for second half of totality. 



Frank Rawes : Read thermometers during eclipse. 



Four Portuguese Soldiers : Handed plate-holders during totality 

 for Mr. Christie and Mr. Davidson respectively. 



The following was the method of procedure, which was carefully 

 rehearsed on several occasions previously. The observers were stationed 

 at their instruments, and Mr. Christie watched the diminishing 

 crescent of the sun on the ground glass of his coronagraph. He 

 had a paper scale on which the lengths of the crescent were marked, 

 computed for the intervals 3 mins., 2 mins., 1 min., 45 sees., 30 sees., 25 

 sees., 20 sees., 15 sees., 10 sees., before totality ; at 15 sees, the length of 

 the crescent was 2'64 inches, and at 10 sees, before totality 2 -30 inches. 

 Having previously given the signal, " Get Ready," Mr. Christie called 

 out " Ten " at 10 sees, before totality, which was the signal to 

 Mr. Dyson to begin the exposures for the "flash." At totality 

 Mr. Christie again gave the signal (the monosyllable " Tup " was used) 

 and Mr. Berry started a metronome which had been carefully rated 

 to give seconds, and proceeded to count up to 50. Mrs. Kennedy took 

 up the count at 51, and continued counting as far as 100, which had 

 been estimated as 10 sees, beyond totality. While the count was 

 proceeding, exposures at the several instruments were made, as described 

 in the separate reports. 



The Day of the Eclipse. It was quite clear in the early morning, but 

 some light cirrus clouds collected later, causing the observers some 

 apprehensions. There was some light cloud in the sky during totality, 



