Mr. Bancroft has divided the architectural remains in Yucatan into four groups, classifying them geographically. We do not consider it necessary to follow such a course, nor enter into the detailed description of any group, but will content ourselves by simply noting any variations from the Palenque models. At Uxmal our attention is at once arrested by the irregular pyramidal base of the building known as the Casa del Gobernador. The base of the pyramid is a figure of an irregular rectangular form. The northern and eastern sides of the base are equal, and measure about six hundred feet each; the southern and western are, however, irregular. As all the angles are right angles, and two contiguous sides are equal, it will be understood that the figure of the base would have been a square, but for the irregularity of the remaining two sides. These irregularities fall within the figure of the square. The pyramid is terraced, the first promenade when observed being but three feet from the ground. The second terrace rises from this to a height of twenty feet, and supports a platform with sides 545 feet in length. A trifle west of the centre of this platform rises the third terrace, nineteen feet high, and supporting the summit platform, measuring about 100 by 360 feet, with an elevation above the ground of upwards of forty feet.[502] The pyramid is composed of fragments of limestone thrown together, but with the terraces substantially faced with walls of regular and smoothly-hewn limestone-blocks, laid in mortar which has become intensely hard. The corners of the pyramid differ from those usually met with in that they are rounded. The terrace walls incline slightly toward the centre of the pyramid. The second platform was reached by a long inclined plain on the south side one hundred feet wide. A regular stairway with thirty-five steps, and one hundred and thirty feet wide, furnished the means of ascent from the second platform to the summit. The crowning feature of the structure is the Casa del Gobernador, a characteristic Yucatan building, measuring three hundred and twenty-two feet long but only thirty-nine feet wide. The Casa is surrounded by a promenade thirty feet wide, and in its interior contains two parallel rows of apartments (a plan of which is given by Mr. Stephens).[503] A sectional view of the Casa resembles the sectional view of the palace corridors at Palenque, except that in the arches conspicuous in the latter, the irregularities produced by the square overlapping stones (which are filled up to an even surface by mortar and plastering), are avoided in Yucatan, by the overlapping stones of the arch being dressed carefully to the angle of inclination of the wall or ceiling, thus presenting a smooth surface. The roof is formed by filling in the space between the tops of the arches and between the arches and the outer walls with stone, up to the desired level; after which a perfectly flat covering