Let fancy lead from Trewsbury Mead,
With hazel fringed, and copsewood deep;
Where scarcely seen, through brilliant green,
Thy infant waters softly creep.
But although the pumping-stations so greedily suck up all the available moisture in summer, the spring is said often to burst out in winter, three feet high; and at such times it is only necessary to drive a walking-stick anywhere into the turf of this meadow for a little fount to spring up from the hole thus drilled.
The river thus originated is known alternatively as the “Isis,” and in the writings of old pedantic antiquaries retains that alternative name until Oxford is passed and Dorchester reached; where, according to such authorities, in the confluence of the Isis and the Thame, the “Thame-Isis,” becomes the “Tamesis,” or Thames. To the Oxford boating-man, however, the streams below and above Oxford are respectively the Lower and the Upper River, and “Isis” is reserved for the title of a University magazine, or the name of a boating-club.
“Isis” is, of course, a Latinised form of “Ouse,” which in its turn is a modified form of the Celtic “uisc,” for water, and gives us such other river-names as Usk, Axe, Exe, and Wye; while we find it hidden again in the names of Kirkby Wiske, in Yorkshire, and in that of “whisky,” deriving from “usquebaugh.”
The time when the Upper Thames was first called “Isis” is uncertain. The name is certainly a Latinised form of “Ouse”; but the Romans do not appear to have so styled it. Julius Cæsar, in his Commentaries, speaks only of “Tamesis”; and the Anglo-Saxon Chronicle, A.D. 905, mentions only the “Thames.” We do not, in fact, read of anything like “Isis” until 1359, when a monk of Chester, Ranulphus Higden, wrote in his Polychronicon a passage which, rendered into English from his Latin original, runs thus: “Tamisa seems to be composed from the names of two rivers, the Ysa, or Usa, and the Thama. The Thama, running by Dorchester, falls into the Ysa; thence the whole river, from its source to the eastern sea, is called Thamisa.” A much later writer, Leland, I think, says, in that rarefied, detached way we expect in old writers, “The common people call it the ‘Thames,’ but scholars call it the ‘Isis.’”
The name of “Thames” is equally Celtic with that of the Latinised “Isis,” nor is it the only Thames in the country, for the river Tamar, dividing Devon and Cornwall; the Teme, in Shropshire and Herefordshire; and the Tame, in Staffordshire, are each closely allied in name.