CELESTIAL DAY OBSERVATIONS. 
125 
nomy, and which have been copied by one writer from another. Observations 
without examination, tend to throw diserace on a science, “P®” P*“* 
whose leading facts and principles have been so accurately esta- the day-time, 
bltshed. 
Observations on Jupiter. 
This planet is very easily distinguished in the day-time, with 
a very moderate magnifying power, when he U not within 30® 
or 40" of the sun. The following extract from my memoran- 
dums may serve as a specimen. August 28th, 1813. ih. 40' 
P. M" saw Jupiter with a power of 15, the aperture not con- 
tracted. He appeared so distinct with this power, that I have 
reason to believe, he would have been perceived with a power 
of d or 7 times. When the aperture was contracted to nine- 
tenths, and afterwards to half an inch, there was little percep- 
tible difference in his appearance. He was then about 58® in 
I longitude east of the sun. 
Though Jupiter, when at, and near his opposition to |he 
nun, appears to the naked eye with a brilliancy nearly equal to 
t that of Venus, yet there is a very striking difference between 
tthem in respect of lustre, when viewed in day-light. Jupiter, 
iwhen viewed with a high magnifying power, in the day-time, 
lalways exhibits a very dull, cloudy appearance 5 whereas Venus 
lappears with a moderate degree of splendour. About the end 
vof June, 1813, between 5 and G in the evening, having viewed 
t the planet Venus, then within 20® of the sun, and which ap- 
fpeared with a tolerable moderate degree of lustre, 1 directed 
t the telescope to Jupiter, at that time more than 32® from the 
ssun, when the contrast between the two planets was very 
sstriking, Jupiter appearing so faint as to be but just discernible, 
I though his apparent magni'ude was more than double that 
tof Venus. In this observation a magnifying power of GO 
\was used. In his approach towards the sun, about the end 
of July, I could not perceive him when he w'as within 15“ or 
116® of his ronjunctiou with that luminary. The.se circum- 
V stances furnish a sensible and popular pnx)f, independent of as- 
tronomical calculations, that Jupiter is removed at a much 
greater 
