Read it through once

Then, again, in mountainous countries where the traveller is continually girdled by amphitheatrical heights; here and there from some lucky point of view you will catch passing glimpses of the profiles of whales defined along the undulating ridges. But you must be a thorough whaleman, to see these sights; and not only that, but if you wish to return to such a sight again, you must be sure and take the exact intersecting latitude and longitude of your first stand-point, else so chance-like are such observations of the hills, that your precise, previous stand-point would require a laborious re-discovery; like the Solomon islands, which still remain incognita, though once high-ruffed Mendanna trod them and old Figuera chronicled them.