395. The metrical value of an initial ῥ which represents ϝρ differs in the several words. It has always the effect of a double consonant in
and nearly always in ῥινός (except Od. 5.281), ῥίζα (Od. 9.390). But lengthening is optional in ῥέζω, ῥιγέω, ῥεῖα, thus we have ἔρρεξα and ἔρεξα (in 27 places); ἵπποι δὲ ῥέα (Il. 8.179), but ἔνθα κε ῥεῖα κτλ.; ἐρρίγησαν, but ὣς φάτο ῥίγησεν δὲ κτλ. As to ῥ- standing for an older σρ-, and the other letters (λ, μ, ν) which lengthen a preceding short vowel, see § 371.