A little problem in Martin Cruz Smith's "Rose"

Now that the long series on avoidable evils and mineral collections is finally complete, I plan a few blog entries on miscellaneous subjects.
      One of the unsung highlights of Tucson in February is the Friends of Pima County annual book sale. There are 100s of thousands of books; some in any category you can think of, although few are technical. I've acquired some unsuspected gems at very low cost, and there are always plenty of novels at $1 each (hardcover) for your airport and summer reading.
     One such summer book was the novel Rose, by Martin Cruz Smith (1996). Smith is mainly known for his Arkady Renko mysteries, but has also written a book on Los Alamos in the early atomic era (Stallion Gate), and some other books I have not read. Most of the ones I have read feature a competent protagonist and an air of hangdog inevitability; no wisecracking supermen here.
     For us geologists, the protagonist of Rose is Jonathan Blair, a mining engineer newly returned to Victorian England from Africa; and the locality is a coal-mining town (and the mine itself). The mystery is resolved underground, and therein lies the rub...
     I have been in old mines (such as the Bell iron mine in Newfoundland) where the ore is moved underground by horse-drawn minecarts. As is logical, the mine tunnels on any level slope down to the mine elevator, so that the "pit-ponies" only have to haul empty carts uphill, and haul loaded carts downhill. For some reason, the tunnels in the Hannay coal mine slope the opposite way: down to the coal workings and up to the elevator. If anyone knows whether this is typical for a coal mine, or just the invention of the author for plot reasons, I'd like to know.