"I have discovered the reference to the Cephisus. It is from Pausanias, 1, 37, 3. I transcribe the passage: you will notice the reference to the Spercheius of the _Iliad_.
"πρὶν δὲ διαβαεναι τὸν Καεφισόν, Θεοδώρου μνῆμά ἐστι τραγῳσίαν ὑποκριναμένου τῶν καθ᾿ αὑτὸν ἄριστα. ἀγάλματα δὲ ἐπὶ τῷ ποταμῷ Μνησιμάχης, τὸ δὲ ἐτερον ἀνάθημα κειρομένου οἰ τὴν κόμην τοῦ παιδὸς ἐπὶ τῷ Καϕισῷ. καθεστάναι δὲ ἐκ παλαιοῦ καὶ τοῖς πᾶσι τοῦτο ῞Ἑλλαεσι τῇ Ὁμήρου τις ἂν τεκμαίροιτο ποιήσει, ἃς τὸν Παελέα εὄξασθαί ϕησι τῷ Σπερχειῷ κερεῖν ἀνασωθέντος ἐκ Τροίας Αχιλλέως τὴν κόμην.
"There can be little doubt that Wordsworth had this passage in mind. The Cephisus is the Attic one; this is a statue, which Pausanias saw on the banks of the river, of the son of Mnesimache cutting his locks over the stream."
Professor Campbell writes:--"The Homeric passage is _Iliad_, 23, 140-151, where Achilles cuts off for Patroclus the lock of hair, which _his father Peleus_ had vowed to the river Spercheius in case of his son's safe return. This is referred to by Plato,--_Rep._ 3, 391 B,--who regards it as an act of impiety to have given that, which was sacred to the river, to a dead body.
"Unless the passage in Pausanias is singularly apposite, I should think that this passage must have been in Wordsworth's mind, and that by a perfectly legitimate use of poetic freedom, in speaking of the later Greek civilisation, he had put the Attic in place of the Phthiotic river."
Since receiving Mr. Heard's letter, I have found that Wordsworth possessed a copy of Thomas Taylor's translation of Pausanias's _Description of Greece_, published in 1794, a copy of that work having been sold at the Rydal Mount sale in 1859. Bishop Wordsworth of St. Andrews has also directed my attention to the following note to Pope's translation of the _Iliad_, a copy of which his uncle possessed. Book xxiii. 175.
"It was the custom of the ancients not only to offer their own hair, but likewise to consecrate that of their children to the river-gods of their country. This is what Pausanias shews in his Attics; _Before you pass the Cephisa_, says he, _you find the tomb of Theodorus_, _who was the most excellent actor of his time for tragedy; and_, _on the banks you see two statues_, _one of Mnesimachus_, _and the other of his son_, _who cut off his hair in honour of the rivers; for that this was in all ages the custom of the Greeks_, _may be inferred from Homer's poetry_, _where Peleus promises by a solemn vow to consecrate to the river Sperchius the hair of his son_, _if he returns safe from the Trojan war_. This custom was likewise in Egypt, where Philostratus tells us that Memnon consecrated his hair to the Nile. This practice of Achilles was imitated by Alexander at the funeral of Hephæstion."