Note 469 — Chapter IV
Walter Armstrong translation
The idea has also occurred to M. Oppert of restricting the ramp to two sides of the tower, to the exclusion of the others (Expédition scientifique, vol. i. p. 209); but so far as we understand his system—which he has not illustrated with any figure—he does not double his incline, he merely alternates its side at each stage, so that part of it would be on the north-west, part on the south-west face of his tower.