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. The generally-accepted source of the Thames at Thames Head has by no means gone undisputed, and a rival exists at Seven Springs, three miles south-east of Cheltenham. This spot is the source of the river Churn, which, falling into the Thames at Cricklade, after a course of sixteen or seventeen miles, takes the stream some ten miles farther up-country than that which issues from Thames Head. Thus we have the singular paradox, that the Churn, this first tributary of the Thames, is considerably longer than the parent stream. This is a problem that would have desolated the logical mind of Euclid, and it has worried geographers and writers of books for uncounted years. No matter how diligently we may seek to track this heresy to its lair—to its original propagation—we shall inevitably be foiled; nor indeed (as in the case of rival religious dogmas) shall we ever be able to definitely settle which of the two is the heresy, and which the true faith. If we rely upon the canon that the source of any river is that point which is situated farthest from its mouth, and then refer to the maps, there can be no doubt whatever that the Churn is the true Thames, and that the Seven Springs source is its head-spring. It is an unavoidable conclusion, like it or like it not; and if we take the trouble to visit Seven Springs, we shall discover that some one has been concerned to mark the spot prominently with the same belief, in the inscription set up there on a wall going down into the pool:— Hic tuus, O Tamesine Pater, Septemgeminus fons. or, in English, Here flows, O Father Thames, Thy sevenfold source.