Fifteen cubits upwards did the waters prevail
Either to such an height above the earth, upwards from that, or from the high hills; for though the words do not necessarily imply that, yet it may be allowed, since there was water enough to cover the highest of them; and fifteen cubits of water were enough to drown the tallest man, or largest beast that should be upon the top of any of them:
and the mountains were covered,
with water, even it may be allowed fifteen cubits high; nor will this furnish out so considerable an objection to the history of the flood as may be thought at first sight, since the highest mountains are not near so high as they are by some calculated. Sir Walter Raleigh allows thirty miles for the height of the mountains, yet the highest in the world will not be found to be above six direct miles in height. Olympus, whose height is so extolled by the poets, does not exceed a mile and a half perpendicular, and about seventy paces. Mount Athos, said to cast its shade into the isle of Lemnos (according to, Pliny eighty seven miles) is not above two miles in height, nor Caucasus much more; nay, the Peak of Teneriff, reputed the highest mountain in the world, may be ascended in three days (according to the proportion of eight furlongs to a day's journey), which makes about the height of a German mile perpendicular; and the Spaniards affirm, that the Andes, those lofty mountains of Peru, in comparison of which they say the Alps are but cottages, may be ascended in four days' compass F15.
F15 See the Universal History, vol. 1. p. 218. marg. Bedford's Scripture Chronology, ch. 12. p. 152, 153.