similar arches: and, as you were told that the moment a bar received an arch heading, it was to be treated as a shaft and capitalled, you will take care to give your bars no capitals nor bases, but to run bars, foliations and all, well into each other after the fashion of cast-iron, as at C. You have still two triangular spaces occurring in an important part of your window, _g g_, which, as they are very conspicuous, and you cannot make them uglier than they are, you will do wisely to let alone;--and you will now have the west window of the cathedral of Winchester, a very perfect example of English Perpendicular. Nor do I think that you can, on the whole, better the arrangement, unless, perhaps, by adding buttresses to some of the bars, as is done in the cathedral at Gloucester; these buttresses having the double advantage of darkening the window when seen from within, and suggesting, when it is seen from without, the idea of its being divided by two stout party walls, with a heavy thrust against the glass. § XVII. Thus far we have considered the plan of the tracery only: we have lastly to note the conditions under which the glass is to be attached to the bars; and the sections of the bars themselves. [Illustration: Fig. XLVII.] These bars we have seen, in the perfect form, are to become shafts; but, supposing the object to be the admission of as much light as possible, it is clear that the thickness of the bar ought to be chiefly in the depth of the window, and that by increasing the depth of the bar we may diminish its breadth: clearly, therefore, we should employ the double group of shafts, _b_, of Fig. XIV., setting it edgeways in the window: but as the glass would then come between the two shafts, we must add a member into which it is to be fitted, as at _a_, Fig. XLVII., and uniting these three members together in the simplest way, with a curved instead of a sharp recess behind the shafts, we have the section _b_, the perfect, but simplest type of the main tracery bars in good Gothic. In triforium and cloister tracery, which has no glass to hold, the central member is omitted, and we have either the pure double shaft, always the most graceful, or a single and more massy shaft, which is the simpler and more usual form.