The falls of the Rhine at Schaffhausen may be compared to them; but these Scandinavian falls are more remarkable in size, as well as more perpendicular.
"Due North or Glimpses of Scandinavia and Russia"
Maturin M. Ballou
The ravine, which was quite wide at its opening, changed into a dell, locked in on two sides by perpendicular rocks, and on its bottom a few trees grew.
"In Desert and Wilderness"
Henryk Sienkiewicz
This method can be used with any fairly perpendicular object, the height of which is known and which is not more than 5 knots away, as Table 33 is not made out for greater distances.
"Lectures in Navigation"
Ernest Gallaudet Draper