MEXICAN OAK-APPLES.--A STREAM LOST IN AN ABYSS.--THE WILD NASTURTIUM.--SPORTSMEN DECEIVED BY CHILDREN.--THE GRAVE-DIGGING BEETLES.--THE COCHINEAL INSECT.--MEXICAN WINE.--GOOD-BYE TO OUR INDIAN HOSTS. As soon as it was light, I awoke Sumichrast and Lucien. L'Encuerado was sleeping so soundly, after his exploits of the night before, that we hesitated to disturb him. I intended to hunt for insects all day, so as to fill up the vacant spaces in the specimen-boxes that Torribio was to take to Puebla; so we bent our steps towards the bottom of the valley. As the inhabitants were still asleep in their huts, Gringalet passed safely all his sleeping brother-dogs with his tail boldly cocked. The winding path brought us out into an extensive hollow covered with verdure. In a hundred paces more, we reached some pyramid-shaped rocks, which were bound together by the gigantic roots of a tree with scanty foliage. The water glided noiselessly through the stones, and disappeared under a low arch shaded by gladiolas, covered with blossoms. Lucien, who was leaning over the opening, wanted to know what became of the water. "Perhaps it is absorbed by sand underneath; perhaps it will reappear in the valleys, where the surface sinks to its level," I answered. "Do streams often go under the ground like this?" "Yes; particularly in Mexico, where these subterranean passages are numerous. Near Chiquihuita, about five leagues from the road which leads to Vera Cruz and Cordova, a large river vanishes into a cave, which is more than three miles in length." "Oh, how I should like to see such a large grotto!" "Your wish shall be gratified, provided we do not lose our way in the _Terre-Chaude_." Sumichrast had only a few minutes left us, when we heard a report, and he reappeared carrying a magnificent bird, whose red plumage had a purple metallic lustre. "We have never met with this fine fellow before," said Lucien. "It is the most brilliant of all the American passerines," I replied--"the _Ampelis pompadora_; but its splendid attire lasts only for a very short time. In a few days its bright-colored feathers fall off, and are replaced by a sombre, dull-looking coat. This moulting, which is common to many birds, has more than once led ornithologists into error, who have described, as a new species, a bird which a new dress has prevented them from recognizing." [Illustration: "The water . . . disappeared under a low arch."] The neighborhood of the _sumidero_ furnished us with a dozen birds of different species; among others, several tanagers peculiar to America, and a pair of pretty light-brown cuckoos, with fan-shaped tails, which are merely birds of passage in this locality. "When you are speaking of a bird, why do you often say it belongs to Brazil, Guiana, or Peru, when you actually find it in Mexico?" asked Lucien.