The shape and ornamentation of the rational varied altogether with the caprice of the artist who designed it. Examples are extremely rare in inventories of cathedral goods, if, indeed, they occur at all. It is probable that they were catalogued together with the _morses_ of copes, with which they were practically identical in appearance. The word 'Rationale' first meets us in the expression 'rationale judicii,' used in the Vulgate _passim_ as a translation of the =to logeion tês kriseôs=, by which the Septuagint expressed the breastplate of the ephod. In the early Church writers the word 'judicii' was dropped and 'rationale' used alone, but always to denote the Jewish ornament. When pseudo-Alcuin wrote, in the tenth or eleventh century, the ecclesiastical rational was quite unknown, for he says: 'Pro rationali summi pontifices, quos archiepiscopos dicemus, pallio utuntur'—a statement which he would certainly not have made if anything less unlike the rational than the pallium had been known to him. Ivo of Chartres, too, knows nothing of the Christian ornament, for although he does not say definitely that the Jewish rational corresponded to the pallium, he says that it corresponded to an ornament _conceded_ (_concessum_) to the chief bishops of his time—an expression which would define the pallium, but certainly not the rational. Honorius of Autun is the writer in whom we first meet with direct and unequivocal mention of the ornament; and he begins his remarks upon it by definitely stating: 'Rationale a Lege est sumptum'—_Lege_, of course, being the Levitical law. This gives us very closely the limits of date between which the rational was assumed—some time between 1100 and 1130. The rational, if we may accept the testimony of the monuments, gradually died out about the fourteenth or fifteenth century. It seems never to have been universal, and an actual rational is one of the rarest ecclesiological treasures a collector can possess. XIII. _The Mitre._—Like that of the _subcingulum_, the history of the mitre is a curious piece of evolution; but, unlike the _subcingulum_, the mitre can be traced through all its history in an unbroken chain of literary references, monumental effigies, and actual specimens. The word _mitra_ (Gk. =mitos=, _a thread_) is applied in the transitional period to a female head-dress, and even St Isidore of Seville makes use of the word in that sense. The Septuagint, however, occasionally translates the expression for the cap of the high priest by =mitra=; at other times they use the word =kidaris=, which they also apply to the cap of the second order of the Jewish priesthood. The Vulgate follows the Septuagint, sometimes using _mitra_, sometimes _cidaris_, and occasionally _tiara_.