Similiter in navibus remi, cum sint sub aqua directi, tamen oculis infracti videntur; et quatenus eorum partes tangunt summam planitiem liquoris, apparent, uti sunt, directi, cum vero sub aqua sunt dimissi, per naturae perlucidam raritatem remittunt enatantes ab suis corporibus fluentes imagines ad summam aquae planitiem, atque eae ibi commotae efficere videntur infractum remorum oculis aspectum.
Similarly in the case of ships, when the oars are put straight in the water, yet to the eyes they seem broken: until their parts touch the topmost level of the liquid, they appear straight, as indeed they are, but when they are let down under the water, owing to the transparent thinness of the element, they send back images flowing from their substance, which float at the topmost level of the water, and being there disturbed, they seem to the eyes to produce a broken appearance of the oars.
final_alignments\Vitruvius_Architecture_Book_6.json