After this he traveled on, without further adventure, until he reached the far western end of the Mediterranean Sea, which was thought to be the end of the world. If you happen to look at a map you will easily find the exact place--it is where the south of Spain very nearly touches Africa. When Hercules arrived there, Spain quite touched Africa, so that one might walk from one into the other. It is said that Hercules himself opened out the narrow passage which lets the Mediterranean Sea out into the great ocean, so that ships could afterwards sail to Britain and all over the world. That passage is now called the Strait of Gibraltar. But the rock of Gibraltar in Spain, and the opposite rock in Africa, between which the Strait flows, are still often called the "Pillars of Hercules." To get from there to Gades was no great distance; and to kill the monstrous ogre Geryon and to seize his flocks and herds for Eurystheus was no great feat after what he had already done. But to drive such a number of sheep and cattle all the way from Gades in Spain to Mycenæ in Greece was not an easy matter. There was only one way of doing so without being stopped somewhere by the sea, and this, as a map will show at once, is by crossing those two great mountain-ranges, the Pyrenees and the Alps--and for one man to drive thousands of sheep and thousands of horned cattle over such mountains as those was the most tiresome and troublesome labor that Hercules had ever undergone. He got as far as Italy without the loss of a single sheep or cow, and was thinking that he saw the end of his trouble. One morning, however, having counted the cattle as usual, and having gone some miles upon his day's journey, he became aware that there was something wrong. The sheep began to bleat and the cattle to bellow in an odd and excited way. And frequently, from behind him, he heard an answering sound which at first he took for an echo. But no, it could not be that, for an echo would have repeated the bleating as well as the bellowing, and what he heard behind him was the sound of bellowing only--precisely like that of Geryon's cows. He counted the herd over again, and, though he was convinced that it was all right at starting, he found a full dozen missing. Now a dozen was not much to lose out of thousands. But he had been ordered to bring back the whole herd, and he would have felt that he would not have done his duty if he, by any neglect or laziness of his own, lost even one lamb by the way. So, following the distant sound, he, with infinite labor, drove his cattle back across the hills, league after league, till he reached a huge black cavern, the mouth of which was strewn and heaped with human bones. His cattle became more excited and more restive, for the sound he was following evidently came from within the cave. He was about to enter and search when a three-headed ogre issued, whose three mouths, when he opened them to speak, breathed smoke and flames.