This is an old book and the style is typical of its time, around the turn of the 20th century. And it is a very very good book, with lots of practical information and little psuedo-scientific gobbldygook that a lot of writers then and now insisted and insist on including. (If I see one more utter misinterpretation of quantum mechanics used to explain things that just don't explain well I will unleash an unaccustomed stream of obscenities.)
I've had this book on my shelves for many years. It is utter nonsense, of course, but fun nonsense.
He WAS getting paid by the word! All the pulp authors were, which is why you find that overblown language in a lot of work from his time.
I actually rather enjoy Merritt and The Moon Pool is a delightfully weird story set in an amazingly weird place. If I have only one criticism of his writing it is that he seems unwilling to write a happy ending. Obviously he read too much Victor Hugo in his misspent youth.