354 THE CASTLE, AND 'THE PROVISIONS OF OXFORD.' colour is entirely due to Copper/ and Dr. Voelcker assures me, that all the examples of antient blue glass examined by him o^Ye their colour to Oxide of Copper. These facts seem to show that there is a real difference in chemical composition, in glass-fictilia from different sources, and that these variations cannot at all times be appreciated by a mere external examination ; hence, then, it is probable that an extensiTe chemical investigation of these, may materially tend to throw hght upon the origin of the different kinds of glass, brought under the notice of the archaeologist, so as to show whether such objects were of native fabrication, or imported. Chemistry may also tend, in the matter of glass, as also in other remains of antiquity, to make us more intimately acquainted with the progress of Art and Invention in times past. Such knowledge moreover, would doubtless assist, in no small degree, in the recovery of lost Arts, or the improvement and advancement of modern manufactures.^ THE CASTLE, AND ' THE PROVISIONS OF OXFORD.' When the Conqueror's survey was made, it does not appear that there existed any military building at Oxford. The mill has continued probably on the same spot down to the present time, from the days of Edward the Confessor ; but the castle adjoining it, is the erection of a later reign. The town was walled round in the middle of the eleventh century, and so were some of the houses, termed mansiones murales, perhaps from being dwellings with the exterior protection of an enclosure by walls. As helping to contribute by this means to the general defence of the place, their occupiers Avere exempted from the pa^^ment of geld, and of all taxes excepting murage, or of attending the King in his expedi- tions. In endeavouring to ascertain the exact date of the castle, we must first of all inquire whether there is any ofiicial record of the Crown that will throw any light as to ' Several specimens of blue Roman - A very interesting series of antient glass have been examined by myself, and beads, in the collection of Mr. B. Nightin- I am indebted to my friend Mr. Alexander gale, is figured in Archaeologia,vol.xxxiv., Williams, M.R.C.S., for analyses of some i. 5. This is almost the first attempt to other examples, the result in all being display the beautiful variety of these alike as regards the presence of copper. ornaments. — Ed.
