188 E. H. BOOTH. 
By this means all plates were satisfactorily ‘“‘over- 
developed’’—that is everything possible was developed out 
on the plate, to the point of general chemical fog. The 
temperature was maintained at from 65 — 70° F. throughout. 
All plates after fixing (Hypo. 1:5) were briefly washed, 
given an alum bath, washed for half an hour, and allowed 
to dry without forcing. 
On examination it was found that the best exposure— 
inner corona, f 64—was 24 seconds. This plate contained 
more detail than those of shorter exposure, and nothing 
had been gained in the 48 second exposure. Owing tothe 
method of development and the latitude of the plates, all 
were quite satisfactory. An exposure of 3 seconds, f 64,. 
was ample for the prominences; in the plate of that 
exposure, No. 1 (consequently showing prominences on 
sun’s eastern limb at second contact), they were fully 
exposed, and developed to maximum contrast. 
The images were quite sharp, prominences and polar 
streamers being excellently delineated. 
The plates from the equatorially mounted aeroplane and 
box cameras were similarly developed. These plates were 
intended to show the outer corona, and to extend the 
streamers as far as photographically practicable. The 
exposures with both cameras were 1, 3, 10, 30, 60, and 36. 
seconds. For the last exposure (36 seconds) the colour 
screen was in position on the aeroplane camera. The 60 
seconds f 63 was definitely overexposed—there was 
evidently nothing to be gained by going beyond 30 seconds, 
which showed a maximum length of streamers (three solar 
diameters). The 36 seconds screened exposure was remark- 
able in so far as the greater portion of general sky illumin- 
ation was cut out, giving much greater coronal contrast. 
The main portion of the coronal illumination was extended 
to a much greater distance than recorded on any of the 
