The dead bull we propped into position with our guns and other supports, and while the artist carefully adjusted his instrument, Shamus began to make preparations for lunch, and Mr. Colon and Semi set out for a few minutes' pastime in catching bugs. They had been gone a full half hour, and we were just remarking their prolonged absence somewhat impatiently, when a loud cry from the nearer bank of the ravine fell on our ears, and looking around we beheld Colon senior, and ditto junior, making toward us at a tremendous rate of speed. "Buffalo!" was all that we could catch of Semi's wild shouts, as he led the chase directly toward us, his father having lost several seconds in securing one of his specimen-cases, and on the instant the old bull that we had wounded an hour before hove in sight, in full charge upon the flying entomologists. As buffalo charges are short ones, he would have stopped, no doubt, in a moment or so, had not Muggs and I, the only members of our party who happened to have their guns at hand, opened fire on him, and planted another bullet between his ribs. The effect was to infuriate the old fellow tenfold, and down he came careering toward us, with what I then thought the most vicious expression of countenance I had ever seen on a buffalo's physiognomy. The attack was so sudden, and the surprise so complete, that we were most ingloriously stampeded, and fell back in hot haste upon our reserves, the guide and teamsters, who, we knew, would be provided with weapons and in good shape to cover our retreat. The sitting for which we had made such elaborate preparations was abruptly terminated in the manner shown in the accompanying engraving. Fortunately for the artist, the blow originally intended for him was delivered upon the legs of the instrument. His assailant being at length dispatched, the poor fellow proceeded to pick out of the ruins of his property what remained that might again be useful. He stated that his stock, as well as the subject of buffalo photographing, was "rather mixed," and that, if we would pay him for the damage done, he would return. Next morning he left us, and thus it was that science lost the projected series of valuable photographic views. [Illustration: TAKING AND BEING TAKEN.] Exploration gives us a past history of the plains which is interesting in the extreme. Our party spent some weeks in exploring for fossils beyond Sheridan, and were richly rewarded. In the great ocean which once covered the land, the wonderful reptiles of the cretaceous age swarmed in prodigious numbers, and their fierce struggles upon and under its surface made "the deep to boil like a pot." The mysterious Leviathan, described in the forty-first chapter of Job, had its prototype in more than one of the monsters of that period: "Who can open the doors of his face? his teeth are terrible round about. "Out of his mouth go burning lamps, and sparks of fire leap out.