As regards the buildings of the Romanesque Period, no subdivision of them can be more satisfactory than that which has already been for some time in use, and which divides them into those which were built before and after the Conquest, and designates them accordingly SAXON and NORMAN. As regards the buildings of that Intermediate Period just mentioned, to none can the term TRANSITIONAL so aptly be applied as to those erected under influences created by that remarkable contest between two great antagonistic principles, which, after having been carried on for a period of nearly fifty years, terminated in a complete revolution in the style of building at the end of the Twelfth Century. Lastly, as regards the Gothic Period, no subdivision of it appears to be so natural and convenient, as that which is suggested by the four principal changes of form through which the Window passed from the Thirteenth to the Fifteenth Centuries. These changes have been fully illustrated by the author in a former work,[C] and will be therefore only briefly recapitulated here. For half a century or more, after the disappearance of the circular arch, the window appeared under a form, which from its general resemblance to a _lancet_, in its length, breadth, and principal proportions, rather than from any uniform acuteness in the shape of its head, led to the universal application of that term to all the windows of this Period. This observation applies equally to the window whether used singly, or in groups of two, three, five, or seven; and equally also to the later as to the earlier examples of this Period. [Illustration: TEMPLE CHURCH.] It is proposed therefore to denominate this the LANCET PERIOD of Gothic Architecture. Towards the close of this Period the practice of combining a plurality of Lancets, under one arch, or hood-moulding--and of piercing the solid spaces that intervened between the heads of these lancets and the underside of this arch in various ornamental ways, became common; by the adoption of which, a group of several lancets was converted into a single window of several lights. Out of this practice arose a novel and beautiful discovery; this was the invention of _Tracery_. [Illustration: CROFT.] For nearly three-quarters of a century after its introduction the Tracery of windows contained forms in which that simplest of all Geometrical figures, the _Circle_, was principally conspicuous: and although, in the latter part of this Period, the Circle does not obtain the same prominent place, in the centre of the window-head, and as the principal feature of the design, that is generally allotted to it in the earlier examples, yet the important part that it bears in the construction of the design of even the whole of these later examples, fully justifies the application of the term, already pretty generally in use, to this class of windows; and entitles us to call this Period after that figure, and "par excellence," the GEOMETRICAL PERIOD.