No. 80: Mar-Apr 1992
Another suggested fluid is sulphur, but there is still room for speculating about exotic fluids, given Venus's high surface temperatures. Another point of interest: the River Styx does not run steadily downhill. It takes an up-anddown course. Either the Venusian topography has shifted since the Styx was cut, or the channel is not a river at all but rather some bizarre geological feature.
(Chaikin, Andrew; "Magellan Pierces the Venusian Veil," Discover, 13:22, January 1992.)