212 
Dr. Herschel‘s Observations 
With 287, 430, and 860, all that has been mentioned be- 
fore is perfectly verified, and confirmed. 
n h 43'. I tried also the lower powers of 172, and 115; 
but they are inferior, in effect, to 215, 287, and 430 ; and not 
adequate to the delicacy and power required in such obser- 
vations. 
I have often taken notice, and again this evening, that the 
illuminated part of Venus is more than a semi-circle. Whe- 
ther the excess of the sun's diameter alone will account for 
this, or how far we are to take the twilight of the atmosphere 
of Venus into consideration, I have hitherto deferred investi- 
gating, as my disk-micrometer wants a moveable parallel, in 
order to be adjustable, by observation, to the quantity of the 
horns which is enlightened beyond an hemisphere. 
May 13, 1793. Correction of the clock, — 3' 28", 4. 
n h 45'. 7-feet reflector; power 115, 172, 215, 287, and 
430. Both horns perfectly alike. No appearance of moun- 
tains. 
The points of the horns appear more blunt than they were 
last night, and are not drawn out to so slender a point ; but 
this is evidently a deception, owing to the indifference of the 
night ; for great sharpness, and distinct vision, are wanting 
in every other object I am looking at. 
May 18. 1793. Correction of the clock, — 3' 33 ",7. 
i2 h 28'. 7-feet reflector ; power 287. Both horns per- 
fectly alike. No appearance of mountains. No spot. But, at 
the present altitude of Venus, it is impossible to make any ob- 
servations that require delicacy, and demand very distinct vi- 
sion with high powers. 
