Does anyone know of a children’s book from the early ’80s which has horizontally split pages like thus –

– whereby each face of the book is graced with a different series of illustrations, each painted such that the bottoms and tops might be mixed together into unusual arrangements? A child peering up in fear fron under he covers of a Victorian four-poster in a darkend room might be married with the top half of a train hurtling over a dark bridge. The cover, I believe, depicts what seems to be a gargle of swans melting into a white puddle of goo. It’s a little disturbing, actually, and formed from two illustrations — one of the swans, one of (I think) some cream being poured into a bowl.
In return, I just rediscovered (and learned the name of) one David Macaulay, author and illustrator of such books as Pyramid, Castle, and Motel of the Mysteries. He’s sort of the Edward Gorey of technical illustration; I used to be entraced by his books, when I was in grade school. Until a half hour ago, he was another victim of my clouded memory — yet now here is is before us all! This has encouraged me that perhaps I might find the other author and book.
The name David Macaulay rang a bell, but I couldn’t place it until you said “technical illustrations”. Then it hit me. I have Unbuilding and The Way Things Work on my shelf and might have read Castle at some point. Oh, I also have BAAA, which I’m confident you would like (looking at a list of titles, it’s probably one of his least technical books.)
Wait a minute. Check that list. Specifically, Black and White. You’ve already answered your own question, silly man.