The prevailing winds and currents in each part of the ocean are well known to us: the exact distance and bearing from one point to another are laid down in the chart; steam bridges over calm areas, and in many cases conducts us on our entire journey at a speed but little inferior to that of land travelling by railroad; modern science preserves fresh and palatable food for an indefinite period; and, in a word, all the difficulties and most of the dangers of long voyages have disappeared. Take one element alone in long voyages--the time required. The average progress of a ship in the eighteenth century was not more than fifty miles a day. Nowadays we may expect as much as four hundred miles in a full powered steamer, and not less than one hundred and fifty in a well-fitted sailing ship. But navigation, and more especially the navigation of the unknown Pacific, was very different in Cook's days, when all the obstacles above mentioned impeded the explorers, and impelled them to follow a common track. There were a few who had deviated from the common track. The Spaniards, Mendana, Quiros, Torres, in the latter part of the sixteenth century, starting first from their colonies in Peru, had ventured along the central line of the Pacific, discovering the Marquesas, certain small coral islands, the Northern New Hebrides, and the Solomon Islands; but their voyages, mainly for fear of Drake and his successors, were kept so secret that no one quite knew where these islands lay. Abel Tasman, in 1642, coming across the Indian Ocean from the westward, had touched at Tasmania, or, as he called it, Van Diemen's Land, had skirted the western coast of the north island of New Zealand without landing, and had stretched away to the north-east, and found the Tonga Group. The English Buccaneers were not among these discoverers; Dampier, Woods Rogers, and others, all went from Acapulco to the Ladrones, looking out for the valuable Spanish galleons from Manila, and they added little or nothing to the knowledge of the Pacific and what it contained. It was not therefore strange that the imagination of geographers ran riot amongst the great unknown areas. They were impressed, as they looked at the globes of the day, with the fact that, while the northern hemisphere contained much land, the southern showed either water or blank spaces; and starting with the ill-founded idea that the solid land in either hemisphere should balance, they conceived that there must be a great unknown continent in the southern part of the Pacific to make up the deficiency. This was generally designated Terra Australis Incognita, and many is the ancient chart that shows it, sketched with a free and uncontrolled hand, around the South Pole. It was held by many that Tasman had touched it in New Zealand; that Quiros had seen it near his island of Encarnacion, and again at Espiritu Santo (New Hebrides), but no one had been to see.