"It may properly be called an inlet of the Indian Ocean," said the Doctor, "as it is long and narrow, and has more the characteristics of an inlet than of a sea. It is about fourteen hundred miles long, and varies from twenty to two hundred miles in width; it contains many shoals and quicksands, so that its navigation is dangerous, and requires careful pilotage. At the upper or northern extremity it is divided into two branches by the peninsula of Mount Sinai; the western branch is called the Gulf of Suez, and is about one hundred and eighty miles long, by twenty broad. This gulf was formerly more difficult of navigation than the Red Sea proper, but recently the Egyptian government has established a line of beacons and light-houses along its whole length, so that the pilots can easily find their way by day or at night." One of the boys asked why the body of water in question was called the _Red_ Sea. The Doctor explained that the origin of the name was unknown, as it had been called the Red Sea since the time of Herodotus and other early writers. It is referred to in the Hebrew Scriptures as _Yam Suph_, the Sea of Weeds, in consequence of the profusion of weeds in its waters. These weeds have a reddish color; the barren hills that enclose the sea have a strong tinge of red, especially at the hours of sunset and sunrise, and the coral reefs that stretch in every direction and make navigation dangerous are often of a vermilion tint. "You will see all these things as you proceed," he continued, "and by the time you are at Suez you will have no difficulty in understanding why this body of water is called the _Red_ Sea." The boys found it as he had predicted, and the temperature for the first two days after passing Perim led Frank to suggest that the name might be made more descriptive of its character if it were called the Red-hot Sea. The thermometer stood at 101° in the cabin, and was only a little lower on deck; the heat was enervating in the extreme, and there was no way of escaping it; but on the third day the wind began to blow from the north, and there was a change in the situation. Thin garments were exchanged for thick ones, and the passengers, who had been almost faint with the heat, were beginning to shiver in their overcoats.