What was that you ask? At the time everyone thought that the cloud shrouded planet was Earth's twin and there could be people just like us there or at least some sort of tropical jungle life.
Venus: he wrote that it would have a hydrocarbon atmosphere and surface temperatures around 800 degrees. He was right. He based this on the Aphrodite legend of springing from her fathers head (Jove). And sure enough there is a mark which could have been left by Jupiter expelling a mass: the Great Red Spot.
The only thing he did not explain is the 3-body problem of Earth, Venus, and the moon in Worlds in Collision. However, others have stepped in to say that all this happened while Earth and Mars were moons of Saturn and the solar system was a very very different place.
See here
The Saturn Myth
Doubleday and Company were the second publisher of Immanuel Velikovsky's first book, Worlds in Collision, after the first publisher, the MacMillan Company felt pressurized into selling. the rights. Doubleday subsequently published all but one of Velikovsky's later books.
Velikovsky's books published by Doubleday 1950: Worlds in Collision ISBN 0-385-04541-7 1952: Ages in Chaos ISBN 0-385-04897-1 1955: Earth in Upheaval ISBN 0-385-04113-6 1960: Oedipus and Akhnaton ISBN 0-385-00529-6 1977: Peoples of the Sea ISBN 0-385-03389-3 1978: Ramses II and His Time ISBN 0-385-03394-X 1982: Mankind in Amnesia ISBN 0-385-03393-1