RamBaut—Rotation-Period of “ Garnet” Spot on Jupiter. 391 
These are :— 
Zenographical Zones. 
Zone. Latitude. Period. 
if + 85° to + 28° Qe bo e120". 
LT. +28 ,, +24 9 542 — ‘to 9" 56e™. 
ei. +24 ,, + 20 9 48 — to 9 492. 
IV. +20 ,, +10 QP ioom ood. 
V. +10 ,, -—12 9°50 20: 
VI. —-12 , -18 9 55 40. 
VIL. -14 ,, —28 9 55 40. (The Red Spot.) 
VEIL. -—18 ,, -37 9] ob iekssls 
IX. —87 ,, -— 585 9 55 5. 
The “Garnet” spot to which our observations relate is 
situated in Zenographical latitude + 13°, and is therefore included 
in Zone IV. of Mr. Williams’ paper. 
The observations were made with the “South” equatorial 
refractor, and the Pistor and Martin’s filar micrometer, which 
contains two movable parallel wires at right angles to a single 
fixed one. The micrometer was set, so that the movable threads 
were parallel to the direction of the system of belts, and the single 
wire set, so as to bisect the equatorial diameter of the planet, as 
Fig. 1. 
represented in figure 1. ‘The wires being kept in this position, 
the time was noted; at which the preceding end of the spot first 
touched the wire, that at which the spot was bisected by the 
SCIEN. PROC. R.D.S., VOL. VIII., PART V. 2F 
on 
