"It has already been stated, that the effect of such glasses in looking at near pictures, is obtainable in a considerable degree without a glass, by making the pictures very large and placing them at a corresponding distance. The rule of proportion in such a case is, that a picture of one foot square at one foot distance from the eye, appears as large as a picture of sixty feet square at sixty feet distance. The exhibition called the Diorama is merely a large painting prepared in accordance with the principle now explained. In principle it has no advantage over the cosmorama or the show box, to compensate for the great expense incurred, but that many persons may stand before it at a time, all very near the true point of sight, and deriving the pleasure of sympathy in their admiration of it, while no slight motion of the spectator can make the eye lose its point of view." _The Colosseum._ "A round building of prodigious magnitude has lately been erected in the Regent's Park, in London, on the walls of which is painted a representation of London and the country around, as seen from the cross on the top of St. Paul's Cathedral. The scene taken altogether is unquestionably one of the most extraordinary which the whole world affords, and this representation combines the advantages of the circular view of the panorama, the size and distance of the great diorama, and of the details being so minutely painted, that distant objects may be examined by a telescope or opera-glass. "From what has now been said, it may be understood, that for the purpose of representing still-nature, or mere momentary states of objects in motion, a picture truly drawn, truly coloured, and which is either very large to correct the divergence of light and convergence of visual axes, or if small, as viewed through a glass, would affect the retina exactly as the realities. But the desideratum still remained of being able to paint motion. Now this too has been recently accomplished, and in many cases with singular felicity, by making the picture transparent, and throwing lights and shadows upon it from behind. In the exhibitions of the diorama and cosmorama there have been represented with admirable truth and beauty such phenomena as--the sun-beams occasionally interrupted by passing clouds, and occasionally darting through the windows of a cathedral and illuminating the objects in its venerable interior--the rising and disappearing of mist over a beautiful landscape, runningwater, as for instance the cascades among the sublime precipices of Mount St. Gothard in Switzerland;--and most surprising of all, a fire or conflagration. In the cosmorama of Regent-street, the great fire of Edinburgh was admirably represented:--first that fine city was seen sleeping in darkness while the fire began, then the conflagration grew and lighted up the sky, and soon at short intervals, as the wind increased, or as roofs fell in, there were bursts of flame