14 Prof. H. H. Turner. 



Dallmeyer Lens and Enlarger. 



Plate 9, January 16, TO, OO, +1-0, + 2'0 positions; O'O the 

 best. 



Plate 10, January 16, O5, + 0'5, + T5 positions ; +0*5 the best. 



Plate 11, January 17, O'O, -f O25, + 0'5, + 0'75, O'O positions. 

 Both O'O exposures were worse than the others. 



Of the others 0'25 was perhaps best near the centre, and 0'5 (or 

 C'75 ?) further from centre. 



Hence 0'5 was adopted, i.e., the object glass was screwed one-half 

 tarn out. The screw has 12 turns to the inch ; and the focussing 

 was thus correct to 0'02 inch, as far as could be judged. 



Abney Lens (continued). 



Plate 12, January 17, 1-0, 0'5, O'O, + 0'5, +VO positions; 

 1-0 best ; 0'5 very good; O'O, + 0'5, +TO distinctly inferior. 



This contradicts nothing but plate 6, on which the exposures may 

 be wrongly identified, and if on that plate O'O is missing instead of 

 -f-0'5, then TO would be the best on the plate. Hence TO was 



[At 25 turns to the inch this focus was also correct to 0'02 inch.] 



8. Programme of Observations. The six slides for photographs of 

 the corona were filled as below, the same plates being used for the 

 Dallmeyer and Abney lenses in each case, and standard squares 

 having been impressed on plates 2, 4, 5, 6, by Captain Hills, R.E., 

 before sending the plates out from England. 



No. of slide. Exposure. Plate. 



1 1 sec. Dry collodion " Gazelle." 



2 5 sees. Ilford " Empress." 



3 10 Rocket. 



4 20 Ilford "Rapid." 



5 1 sec. Ilford " Empress." 



6 2 sees. Ilford " Empress." 



Besides these the two exposures through the polariscopic apparatus 

 were made, each of 5 seconds' duration, Paget plates being used. 



The developer used was amidol for all these plates, which were 

 all successfully exposed. 



9. Times of Contacts. These were independently observed by 

 Professor Turner and by Major Burrard, R.E. The former used for 

 first and fourth contacts a pocket watch which was compared with 

 the sidereal clock at 8.5 A.M. and found 29 seconds fast ; and again at 

 8 P.M., and found 26*9 seconds fast, of local mean time. At second 

 and third contacts he gave a sharp signal, the time of which was 



