Total Eclipse of the Sun, 1901, May 18. 259 



developing the photographs was almost entirely carried out by Mr. 

 Walter and by Mrs. Maunder, to whom the expedition is therefore greatly 

 indebted for the results obtained. The weather being hot and damp, 

 much difficulty was experienced with the different plates tested by way 

 of experiment before the day of the eclipse. Finally the following 

 developer was adopted and found to work well. In spite of its 

 excessive dilution, it was found that fog resulted if its strength was 

 materially increased. 



Solution A. 



Metol 40 grains. 



Hydroquinone 50 



Sulphite of soda 120 



Bromide potassium 15 



Water 20 ounces. 



Solution B. 



Caustic soda , 100 grains. 



Water 20 ounces. 



For development half an ounce was taken of each stock solution and 

 made up with water to 30 ounces, 15 drops of a 1 per cent, solution of 

 bromide of potassium being added. During development this solu- 

 tion was strengthened by the gradual addition to it of a solution com- 

 posed of 1 ounce of each of the two stock solutions made up with 

 water to 10 ounces. But the stronger solution was seldom added to 

 the weaker in a greater proportion than 1 to 15. The average time 

 of development was 75 minutes. 



Photographs of tlie Partial Phase. These were taken with the photo- 

 heliograph of the Royal Alfred Observatory, Mauritius, already 

 described. The aperture for this purpose was reduced to 1|- inches, 

 and the exposure given by the drop-slit in the primary focus. Mr. 

 T. F. Claxton made the exposures, and called the times by Kullberg 

 3400 to Bombardier Cox, who entered them. There being only three 

 plate -carriers available for this work, Mr. C. Garrioch remained in the 

 dark room to change the plates, and Bombardier Truman ran to and 

 fro with them. The plates used were Cadett and Neale's ordinary 

 lantern plates. The times of exposure were as follows : 



