Voyager 1 and 2 narrow-angle frames were used to obtain displacements of features at resolution of 130 km over time intervals of 1 Jovian rotation. The zonal velocity ? was constant to 1.5% during the 4 months between the Voyager 1 and 2 encounters. The latitudes of zonal jet maxima (extrema of ?) are the same as inferred from earth-based observations extending over the past 80 years. The curvature of the velocity profile d2?/dy2 varies with latitudinal coordinate y in the range from -3&bgr; to +2&bgr;, where &bgr; is the planetary vorticity gradinet. The barotropic stability criterion is violated at about 10 latitudes between ¿60¿. The eddy momentum flux variation with latitude ?'?' is positively correlated with d?/dy for both Voyager 1 and 2 data. The rate of conversion {K'?} of eddy kinetic energy into zonal mean kinetic energy is in the range 1.5--3.0 Wm-2, for a layer 2.5 bar deep. The time constant for resupply of zonal mean kinetic energy by eddies is in the range 2--4 months, less than the interval between Voyager encounters. The rate of energy conversion is more than 10% of the total infrared heat flux for Jupiter, in contrast with earth where it is only 0.1% of the infrared heat flux. This hundred-fold difference suggests that the thermomechanical energy cylcles are very different on the two planets.