Garrett Putman Serviss 
Columbus of Space 

A group of friends travel to Venus in a "car" (the author deliberately avoids calling it a ship) constructed by one of their number, a scientist with a brilliant mind, who – like the author himself – has always been explaining scientific and other complicated facts to his lesser gifted friends. The car runs on nuclear power, and their aim is Venus, because their guide is certain of the planet’s habitability. At that time, Venus was still thought to rotate in a way that it would always show the same hemisphere to the sun, making it a planet divided into one half of eternal darkness and one of eternal sunshine. That is what the friends find, and of course the inhabitants of the two sides differ accordingly. They arrive on the dark side, and have some adventures there; but the larger and more adventurous part of the story takes place on the sun side, where they venture later. After having crossed crystal mountains and vast stormy oceans, they reach the land of a people of such a high degree of civilization that spoken language has almost completely been replaced by telepathy. Of course, the scientific leader of the group does not take long to learn that language, and makes many astonishing discoveries. (Goodreads)