During the Imperial period, the Romans took great delight in witnessing representations of fights at sea, and their emperors were equally fond of exhibiting them. The first spectacle of this kind, or _naumachia_, was given by Julius Cæsar upon a lake dug for the purpose in the Campus Martius. Augustus caused a lake or "stagnum" to be made for a similar use. This remained as the permanent scene of such exhibitions. The combatants in these fights were usually captives or criminals condemned to death, who fought as in gladiatorial combats, until one side was exterminated or spared by imperial clemency. In a naumachia given by Nero, there were sea-monsters swimming about in the artificial lake. Claudius ordered a naval battle upon Lake Fucinus, in which one hundred ships and nineteen thousand combatants were engaged. Troops of nereids were seen swimming about, and the signal for attack was given by a silver Triton, who was made, by means of machinery, to blow the alarum upon a trumpet. We now proceed to narrate, in chronological order, the very few voyages of discovery made previous to the Christian era. These were those of Hanno to Sierra Leone, of Sataspes to Sahara, of Nearchus from the Indus to the Tigris, of Pytheas from Massilia to Shetland, and of Eudoxus from Cadiz to the Equator. [Illustration: THE COMMON PENGUIN.] CHAPTER VII. THE VOYAGE OF HANNO THE CARTHAGINIAN--HE SEES CROCODILES, APES, AND VOLCANOES--THE VOYAGE OF HIMILCON TO AL-BION--THE VOYAGE AND IGNOMINIOUS FATE OF SATASPES THE PERSIAN--THE VOYAGE OF PYTHEAS THE PHOCIAN--THE SACRED PROMONTORY--A NEW ATMOSPHERE--AMBER--RETURN HOME--THE VERACITY OF PYTHEAS' NARRATIVE--THE EXPEDITION OF NEARCHUS THE MACEDONIAN--STRANGE PHENOMENA IN THE HEAVENS--THE ICTHYOPHAGI--HOUSES BUILT OF THE BONES OF WHALES--FISH FLOUR--A BATTLE WITH WHALES--AN UNEXPECTED MEETING--THE DISTANCE TRAVERSED BY NEARCHUS--THE VOYAGE OF EUDOXUS ALONG THE AFRICAN COAST--STATE OF NAVIGATION AT THE OPENING OF THE CHRISTIAN ERA.