Total Eclipse of the 8nn as observed at Ovar, Portugal. '!07 



exposed us below, the exposures being given by the observer with the 

 exposing shutter of the plate-holder, and the times noted by him, 

 counting from the commencement of totality. 



Plate. 



Lantern 12 in. x 10 in. 



Empress 12 x 10 



SandeU's Triple-coated 15 x 15 



Special Rapid 15 x 15 



Lantern 12 x 10 



As soon as possible after totality a second plate was put in No. 5 

 plate-holder, and exposed twice on the sun for orientation (with driving 

 clock stopped for 3 min. between), the exposure being as short as 

 possible (i to | sec.), and the aperture reduced to 2 inches. 



" Abney squares" were put on Nos. 1, 3 (twice), and 5, after return 

 home. 



No. 1 300 s exposure at 5 ft. to standard candle. 



No. 3 ...5 s and 30 5 



No. 5 300 3 



The plates were all developed after return home, hydroquinone dilute 

 being used. Nos. 1 and 5 unfortunately blistered badly in develop- 

 ment, especially No. 1, though every care was taken, the developer 

 being at a temperature of 60. It is to be remarked that other plates 

 developed at the same time under precisely similar conditions were 

 free from blistering. No. 2 is to a certain extent disfigured with spots 

 on the plate, which, however, do not materially interfere with the 

 coronal detail. 



No. 4 shows fine detail in the polar plumes and coronal streamers 

 extending to nearly a diameter of the Sun from the limb. No. 3 shows 

 nearly the same. 



No. 5 shows very fine detail in the prominences in the S.W. quad- 

 rant, with gradation of brightness merging into the coronal structure 

 close to the limb, thus showing a continuity between the two pheno- 

 mena, and affording fresh evidence of the association between coronal 

 streamers and prominences, which was indicated in the photographs of 

 the 1898 eclipse. 



It should be mentioned that the coronagraph was carefully focussed 

 in the same manner as for the eclipses of 1896 and 1898,* by means of 

 the image of an object (gauze net) in the plane of the plate reflected 

 from the plane mirror of the ccelostat. The focus was thus obtained 

 with great accuracy after two or three trials, and it was found that the 

 field was remarkably flat. 



* ' Monthly Notices R.A S.,' vol. 57, p. 105 ; ' Eoy. Soc. Proc.,' vol. 64, p. 8. 



