What about Terra Australis?
Why write about a parallel 18th century world instead of the real one?
Certainly, we’re not against doing research in our world to use in that other world we’re creating. In fact, we very much enjoy it. The historical 18th century provides physical structure– real ships, period technology, even period ideas, upon which we can build. Thus, we take real places like England and France, and real political situations, like the struggle between France and England. Then we add something theoretical from the 18th century– Terra Australis, and we make it (selectively) real.
We say selectively real because, on the one hand, we’ve based it on the actual Antarctica, but, on the other, we’ve changed its climate and we’ve populated it. We have made much of it green, and only some parts, ice. By doing this, we have generated a strong plot element: why is this place, Terra Australis, cold in one place and warm in another? Is it possible that someone or something creates that cold? And, if so, are we on our way to mystery and villains?