30 Dr. Herschel's Observations of a 
e y e -gl as s, as it can in a convex one ; whereas with the latter, it 
is well known that such a motion of the eye can be of no use. 
2 h 36'. 20-feet reflector ; power 157, 300, 4,80. I see the 
quintuple belt very well. 
We know that the planet Jupiter has many belts. Some re- 
markable instances of their being very numerous are recorded 
in my journal, one of which is accompanied with a figure. The 
observations are as follows : 
May 28, 1780. Jupiter's belts are curved ; and there are a 
multitude of them all over the body of the planet. See fig. 2. 
Jan. 18, 1790. I viewed Jupiter with the 40-feet reflector. 
There were two very dark, broad belts, divided by an equa- 
torial zone or space, the colour of which was of a yellow cast. 
Next to the dark belts, on each side, towards the poles, were 
bright and dark small belts, alternately placed, and continued 
almost up to the poles, both ways. 
In taking out fig. 2. from my journal, I perceive one so very 
unlike it just before, that I am induced to give it here, though 
rather foreign to my present purpose. It contains, however, 
an observation which it will not be amiss to record. 
April 6 , 1780. I had a fine view of Jupiter, and saw, as soon 
as I looked into the telescope, without having any previous 
notice of it, the shadow of the 3d satellite, and the satellite it- 
self, upon the lower part of the disk. See fig. 3. The shadow 
was so black and well defined, that I attempted to measure it, 
and found its diameter by the micrometer i",5b2. 
This measure of the shadow should be checked by the fol- 
lowing observation. 
March 15, 1792. n h 54'. With the 20-feet reflector, and a 
power of 800, I estimate the apparent diameter of the largest 
