"In order to obtain a notion of the size and solid excellence of the work, it will be well first to make the circuit of the entire edifice. We shall thus have an opportunity of admiring the fine distribution of the different masses. After the first circular wall or belt, which rests upon a base of travertine, has attained a height of nearly forty feet, it is finished off with a simple cornice, serving as a solid foundation for the second belt. As a preservative against sinking, this is, moreover, provided with a series of larger and smaller construction arches, alternating symmetrically with one another. After rising some thirty feet, further solidity is given to the wall by a girdle suitably decorated with consoles, and on this the third belt (which is but a few feet lower) is supported. A similar number of the arches already mentioned, introduced as frequently as possible, enables this wall to support the weight pressing upon it, and to raise the harmoniously rounded cupola boldly aloft. "In ancient times the whole building, which is composed of brick, was covered and embellished with a coating of stucco. On the upper cornice, at the back, between the consoles, portions of terra-cotta decorations still remain, seeming to have formed part of this ornamental facing. "In our examination of the interior, we are, unfortunately, much hindered in our attempt to investigate the constructive connection of the whole by the unmeaning ornamental additions, and the thoughtless transformation of the different organic masses. [Illustration: INTERIOR OF THE PANTHEON.] "So much, however, may be discovered even on a superficial survey--namely, that the architect has everywhere endeavoured, not merely to diminish the pressure on the walls of the lower belt (which is nearly twenty feet thick) by inserting hollow chambers, but has given them additional strength by means of the vaulted constructions thus introduced. A hall, supported on pillars, lies between each of the eight modern altars, and behind each of them, on the outside, are niches, reached through the different doors, recurring at regular distances throughout. "The slabs of coloured marble belonging to the attica were carried off some hundred years ago, under Benedict XIV., and their place supplied by the present coulisse paintings. This polychrome system would have greatly facilitated our researches into the coloured architecture of the ancients, and its loss is therefore much to be regretted. "For, although this portion of the edifice was thus transformed at a comparatively late period, still the effect of those finely harmonized masses must have been a remarkable one.