68 RECENT CHANGES IN THE SURFACE OF JUPITER. 
Next to the great girdles which encircle Jupiter, “the red 
— is certainly the most remarkable feature me has ever been 
etected upon it; 30,000 miles long, by 8,500 miles wide, it 
covers a surface very much greater than that 2 te whole of the 
earth, and is easily seen with good telescopes, but ina 
red, and why a different red from any other marking, are questions 
not yet answer 
It is generally looked upon as a recent marking, and I have 
been at some trouble to trace its history, and shall I be beable 
to show you that it is much older than many suppose. The 
published account of it is by Mr. F. C. Dennett, in the “ English 
Mechanic” for 1879, page 277 ; he there asks if any one had seen 
a pink-coloured patch on the south temperate zone of Jupiter, 
which he had many times observed, and saw for the first time on 
July 27, 1878. From a letter in the “ Observatory” for Januaty 
1879, it appears that Mr. Pritchett saw the same marking first 
on J uly 9th, 1878 ; since then there have been many letters on the 
subject, but I have not seenany earlier date mentioned thanJuly 9th. 
On referring to my own drawings and notes I find that 1 first saw it 
separated from the belts on July 8th, 1878; it was then a faint 
and difficult object to see, but m drawing gives jt a form | 
recognising it as an old friend that I had re 
with one made November 2 2, 1880. ‘The drawings are all careit 
made, estimating the siz e of each marking compare ~ with 
whole planet, so that ‘east may be put on the paper cl st 
as possible ; and I find, on comparing them, that P they ee 
in accord, so much so that I have mines in the dimensions 
the north side of os spot would be a little more, cm the pe 3 | 
not changed. eee ys comparing the et June 2 bet 
with others, I found I had drawn it in the same pe riod 
11, 1880; and taking the most recent ° value -of shal! jt bas 
rotation, it exactly measured this interval, showing ta" 
