THE COLOURS OF JUPITER'S BELTS. 79 
30th September occurred an opportunity seldom to be met with, for 
about 9h. to 9h. 30m. the conditions for observing were absolutely 
perfect with a power of 500, which the mirror bore with ease ; 
north and south polar shadings were seen to consist of hundreds 
upon hundreds of the minutest belts, but so fine were they and so 
close together that the slightest tremor of the atmosphere sufficed 
to merge them into each other. I tried the experiment several 
times of placing my warm hand against the outside of the tube, 
and the slight disturbance of the air inside caused by this instantly 
obliterated them. It was a beautiful sight, and a fine testimony to 
the excellence of Mr. With’s mirror. 
have confined these few remarks chiefly to the colours of the 
various features of the planet ; in other observations connected with 
it, abler hands than mine have doubtless turned this opposition to 
account. 
