As, after completing the circuit of the mounds, there were still a few hours at my disposal before leaving Palenque so as to reach the village before nightfall, I decided to devote the time to the investigation of certain problems regarding the age and construction of the buildings. But in the first place, attention should be directed to the manner in which the open courts within the monastery are disposed, and access is obtained to the rooms beneath the corridors. Commencing from the east front, there are two ranges of corridors which are separated throughout their whole length by a strong wall, which receives the thrust of the two inner slopes supporting the roof. There is only one entrance or means of communication between them in the existing northern portion of the ruins. The interior width of each of these galleries is about seven feet four inches. After passing across them, the principal court is reached and the floor of the open space is seen ten feet below. A wide flight of large and well hewn stone steps leads down to the bottom, which appears to have been paved with several layers of cement. This court is twenty-eight paces wide. The rooms are entered through doorways in the sides of the inclosing walls. Opposite to the first flight of steps there are similar steps leading to a second series of corridors. Passing through these, another court is reached, and beyond is the outer gallery which runs along the western side of the building. The total width of this cross section of the monastery is approximately one hundred and seventy-six feet. [Illustration] When wandering amongst these courts, and looking at the vestiges of an unknown state of civilisation, I endeavoured to form conclusions with regard to the purpose and antiquity of all that was seen. The problem is difficult to solve. It has been surmised that the temples of Palenque were erected during a period not exceeding four centuries before the Spanish conquest. This opinion was based upon what has been observed with respect to the condition of the ruins, and the freshness of portions of the colouring of the stucco. This method of estimating comparative antiquity presents some local difficulties.