The brushwood covering the ground was made brilliant by numerous fireflies. The light which shone from these beetles far exceeded anything of that nature that I had seen in other regions, and I took the opportunity of ascertaining the strength of the illuminating power. I sent one of the men into the wood to catch the largest firefly that he could find, and then, after having made the corridor dark by extinguishing our candles, the insect was held about two inches from a blank page of my note book, Dr. Coller watched the experiment. We found that the light was steady and shed a soft clear phosphorescent glow over the paper. The luminous power was sufficient to enable us to read or write with ease over a surface two inches square. After writing a few notes upon what had been done during the day we added:— “Written by the light of a firefly in the Palace, in the ruins of Palenque, the night of Wednesday, March 10th, 1870, the candle (firefly) held by Dr. Albert Coller. The light about equal to that of a small wax candle and very pure. The light rather greenish.” “Dr. A. J. COLLER.” Before turning into my hammock I visited the horses tethered at the base of the mound near the stream. They were much worried by flies, mosquitos, and small ticks called garrapátas, which find their way under the skin and cause great irritation. In the corridor, thirty feet above them, we were not troubled with any of these pests, but there were numerous bats. The Indians said that, sometimes, horses were seriously injured by bats biting them above their hoofs. In the morning, upon the earliest indications of dawn, the solitary nightingale again began its song, and the clear staccato, and singularly musical note was again heard amongst the ruins until sunrise, when it ceased. Thus this bird sang its song of praise as the herald of the day.