It may appear strange, yet it is now well known to be the fact, that although the small width of the Isthmus was ascertained soon after the discovery of America, its natural features remained entirely unknown for three hundred years. Robertson, in his History of America, states that the Isthmus is traversed in all its length by a range of high mountains, and it was reserved for our scientific countryman, Lloyd, who surveyed the Isthmus in 1828 and 1829, by direction of Bolivar, then president of the Republic of Colombia, to dispel the illusion. From his observations, confirmed by more recent travellers, it is now ascertained that the chain of the Andes terminates near Porto Bello to the east of the Bay of Limon, otherwise called Navy Bay, and that the Isthmus is, in this part, throughout its whole width, a flat country. It was also long supposed that there was an enormous difference between the rise and fall of the tide in the Pacific and Atlantic Oceans on either side of the Isthmus, and that the opening of a communication between the two seas would be productive of danger to a large portion of the American continent. It is now, however, ascertained that the difference of altitude is very trifling, not more than thirteen feet at high water.[5] The prevalence of these errors may have tended, in combination with Spanish jealousy, unhealthiness of climate on the Atlantic side, the denseness of the forests, and the unsettled state of the Government for some years after the Spanish yoke was shaken off, to prevent the undertaking now proposed from being seriously considered. Panama is the principal city on the Isthmus. Its site has been once changed. When the Spaniards first visited the Isthmus in 1512, the spot on which the old city was afterwards built, was already occupied by an Indian population, attracted by the abundance of fish on the coast, and who are said to have named it "Panama" from this circumstance, the word signifying much fish. They, however, were speedily dispossessed; and even so early as 1521, the title and privileges of a city were conferred on the Spanish town by the emperor, Charles the Fifth. In the year 1670, it was sacked and reduced to ashes by the buccaneer, Morgan, and was subsequently built where it now stands. The position of the present town of Panama is in latitude 8° 57' N.; longitude 79° 30' W. of Greenwich, on a tongue of land, shaped nearly like a spear head, extending a considerable distance out to sea, and gradually swelling towards the middle. Its harbour is protected by a number of islands, a short distance from the main land, some of which are of considerable size, and highly cultivated. There is good anchorage at each of these islands, and supplies of ordinary kinds, including excellent water, which may be obtained from several of them.[6]