Grantchester Church is chiefly noteworthy for its singularly beautiful chancel, an almost ideal example of fourteenth century work, perched most effectively above one of the bends in the road. The name, with its "chester" has led many antiquarians to hold that here was a Roman station.[165] But the application of the name to the village is only some three centuries old. In earlier days it is always "Grantset." We do find "Grantchester" in Bede (as mentioned in our account of Ely); but the spot indicated is almost certainly Cambridge, then still in ruins after its destruction during the English conquest of Britain. [Footnote 165: "Chester," "Caster," "Cester," are various Anglicised forms of the Latin "castra" (= camp), which our conquering forefathers applied to the Romano-British cities which they so ruthlessly destroyed in the first sweep of their invasion.] On the top of the church-tower here we may notice a weird-looking piece of iron work. This was put up in 1823 to facilitate the astronomical work in the University Observatory, as it is exactly south of the telescope dome there, two miles and a half away. With the acquisition of collimating telescopes, in 1869, this relationship ceased to be of value, and now the growth of trees has rendered the tower wholly invisible from the Observatory. Not far from Byron's Pool we find the watersmeet of the two main streams which make our Cambridge river; each so equal in size to its sister that neither can be called the tributary of the other. The name Granta is usually appropriated to the eastern stream, that of Cam to the western. On some maps the latter is called the "Rhee," but this (like the Isis at Oxford), is merely a map-maker's name.[166] [Footnote 166: On the western bank, hard by, is a large meadow known as Lingay Fen, which is always (artificially) flooded during the winter, in hopes of a frost. It forms an excellent skating ground, on which even National Championships have been decided.]