Misc: who was the captain in 20,000 leagues under the sea??

Questions

U.S. launches Pioneer Venus probe.?

B.C. Persia defeats Spartan king Leonidas at Thermopylae.?

Battle of Dupplin Moor (in Scotland).?

Izaac Walton, fisherman, writer (Compleat Angler), born.?

Amedeo Avogadro, made famous by picking 6.022 x 10 ^ 23?