"In the course of my inquiries, I heard that Messrs. Chance and Co., of Birmingham, had just introduced from the Continent the manufacture of sheet glass. Accordingly, I went to see them make this new article, and found they were able to manufacture it three feet in length. I was advised to use this glass in two lengths, with one overlap; but to this I could not assent, as I observed, that since they had so far advanced as to be able to produce sheets three feet in length, I saw no reason why they could not accomplish another foot; and, if this could not be done, I would decline giving the order, as, at that time, sheet glass was altogether an experiment for horticultural purposes. These gentlemen, however, shortly afterwards informed me that they had one person who could make it the desired length, and, if I would give the order, they would furnish me with all I required. "It may just be remarked here that the glass for the Exhibition Building is forty-nine inches long--a size which no country except England is able to furnish in any large quantity, even at the present day. "In 1840 the Chatsworth Conservatory was completed and planted. The whole length of this building is 277 feet; its breadth, 123 feet over the walls; and the height, from the floor to the highest part, 67 feet. "Notwithstanding the success which attended the erection of these buildings, it became to me a question of importance how far an extensive structure might be covered in with _flat_ ridge-and-furrow roofs; that is, the ridge-and-valley rafters placed on a level, instead of at an inclination, as in the green-house, or curvilinear, as in the Great Conservatory. I therefore prepared some plans for an erection of the kind for the Earl of Burlington, somewhere about ten years ago; but, on account of the lamented death of the Countess, the design of erection was abandoned. However, from that time I felt assured, not only that it could be done satisfactorily, but that the most appropriate manner to form and support level glass roofs, to a great extent, was that adopted this year for the New Victoria House at Chatsworth, which may be considered a miniature type of the Great Industrial Building. "Before describing this house, however, it may be well to notice two instances in which the flat roofs had been previously tried, and in both cases with the most perfect success. "The first of these was a conservatory attached to a villa in Darley Dale, only a short distance from Chatsworth. This building is divided into five bays, with a glass door in the centre, and glass pilasters separating the bays; the ridge-and-furrow roof covers an opening of seventeen feet in the clear. The ventilation is simultaneously effected by a lever connected with a rod, which is attached to all the ventilators.... [Illustration: THE VICTORIA REGIA HOUSE, CHATSWORTH.]