210 
Dr. Herschel's Observations 
that part which divides the enlightened, from the unenlight- 
ened part of the disk. With 400, appearances are the same. 
g h 1 6'. The bright part, on the limb of Venus, is like a 
bright bead, of nearly an equal breadth all around. 
April ib, 1703. Correction of the clock, — 2' 59", 5. 
1C)h o ' • 7-feet reflector, with different powers. No spot 
upon the disk. No mountains visible. Both horns alike. 
A luminous margin, as usual, all around the limb. 
April 20, 1793. Correction of the clock, — 3' 3", 8. 
io h o'. 7-feet reflector ; power 172, 213, 287, 430, and 
8bo. No spot upon the disk. Both horns exactly alike. Not 
the least appearance of any mountains. 
With 287, there is a narrow luminous border all around the 
limb, and the light afterwards diminishes pretty suddenly, and 
suffers no considerable diminution as we go towards the line 
which terminates the enlightened part of the disk. It is how- 
ever less bright near the terminating line than farther from it. 
With powers lower than 287, the narrow luminous border 
cannot be so well distinguished. 
April 22, 1793. Correction of the clock, — 3' 5", 9. 
9 h 30'. 7-feet reflector ; power 430. Very distinct. No spot. 
No appearance of mountains. Both horns perfectly alike. 
With 860, 1290, and 1720, not the least appearance of 
mountains. Even the last power is considerably distinct. 
io h 20'. With 430, the luminous margin, compared to the 
light adjoining to it, may be expressed by, suddenly much 
brighter all around the limb. 
April 28, 1793. Correction of the clock, — 3' 12", 3. 
i2 h o'. 7-feet reflector ; power 215. No spot. Both horns 
perfectly alike. No appearance of mountains. 
