Which preposition to use with deaw

of Occurrences 2%

"For not to have been dipt in Lethe lake, Could save the sonne of Thetis from to die; But that blinde bard did him immortall make 430 With verses dipt in deaw of Castalie: Which made the Easterne conquerour to crie, O fortunate yong man!

Which preposition to use with  deaw