What is another word for "deepen"?

Roget's Thesaurus (1911) lists these synonyms for "deepen": abysmal, accession, accretion, add, additional, advance, aggrandize, aggrandizement, aggravate, aggravation, ahead, and, ankle, ascend, ascent, augment, augmentation, bathometer, bathymetry, benthal, beyond, bottomless, cast, concavity, crater, crescendo, deep, deepness, depression, depth, development, dig, dilatation, dilate, disperse, dispersion, draught, earth, enhance, enlarge.