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XLIX. 
ON THE ROTATION-PERIOD OF THE “GARNET” SPOT 
ON JUPITER. By ARTHUR A. RAMBAUT, M.A., D.Sc., 
F.R.A.S. 
[Read Marcu 18; Received for Publication Marcn 20; 
Published June 30, 1896.] 
Osservations of Jupiter’s telescopic appearance have been 
especially interesting during the present opposition of the planet, 
on account of the conspicuous markings which have been deve- 
loped on its surface since it was lost to sight in the Sun’s rays. 
When Jupiter reappeared last autumn from conjunction, it was 
found that two new, well-defined, dark spots had broken out in 
what is known as the north tropical zone. These seem to have 
been first observed by M. Antoniadi of the Observatory of 
Juvisy, who, writing tothe Bulletin de la Société Astronomique de 
France, describes the second—the following—of these as “ rouge 
grenat trés foncé,” and says that on October 15th it was so 
dark that it might have been taken at first for the shadow of a 
satellite. 
In respect of shade, this spot is quite remarkable, standing out 
more distinctly than any of the other markings on the disc, and 
has, as a matter of fact, been mistaken by more than one observer 
(who on looking at the planet was unaware of its existence) for 
the shadow of a moon, until a reference to the Ephemeris showed 
that none of the moons were in a position to cast such a shadow 
at the time. 
This spot covers about 5°°5 in zenographical longitude, and 
about half that in latitude, and is of a very well-defined oval 
form. Its actual linear dimensions are about 4200 miles long 
by about 2000 miles broad. 
