As I shall have more to say on the subject of windows when we come to secular architecture, I will limit myself to two remarks. One is this; that in positions in which there is not much height, where there is no great load to be sustained, and where the termination of the wall internally and externally is horizontal, the Mediæval architects by no means held themselves bound to the arched form, but reserved perfect liberty to put square heads to their windows; the other is a passing remark on the _rationale of stained glass_. I do not conceive it to be simply a decoration or a means of adding rich colouring, but that it also arose from an unconscious feeling that it was necessary to the perfect effect of an architectural interior that it should be _self-inclosed_. In a living-room one wishes not only for admission of light, but for facility of looking out at the windows; and this necessity prevents us from seeing the windows well as architectural features, because the focus of the eye has constantly to be changed in passing from the window itself to the view beyond. In a church, on the contrary, you do not wish to look out at the window, and it is better that it should be filled with a medium only semi-transparent, and which, being at about the same distance from the eye with the surrounding architecture, at once does away with the necessity of a change of focus, and supplies a beautiful decoration to the medium by which that object is effected. I have not yet noticed one of the leading features of the style, and one in which it assumes a character most peculiarly its own: I mean the _roof_. All previous styles of architecture with which we are acquainted, having originated in Southern countries, had roofs of a low pitch. I have no doubt that in many of those countries there were occasions in which a higher pitch would have answered better; but as the lower line harmonised better with the generally horizontal lines of their architecture, and was found to answer, they naturally adopted it. The Romanesque architecture of Southern Europe had also somewhat low roofs, and when first imported into Germany the roofs were by no means high. Gradually, however, as men forgot its connection with Italy, and viewed it as belonging to themselves, they would naturally use with it the form of roof they had found most serviceable and were most accustomed to in their ordinary buildings; and thus the high roof of the North became engrafted upon the Romanesque style, and became conspicuous feature in external architecture. Happily this change harmonised well with its general character. The arch seemed to suggest a higher pitch of roof than did trabeated construction, and when greater height was generally introduced, and the pointed arch took the place of the round, the high pitch of the roof would be found better to harmonise with it.