The Doctor explained that the modes of making these bottles had changed very little in five thousand years, as they could see by the pictures on the walls of the tombs. The ancient Egyptians were familiar with the wheel and its uses; the potter of the time of Rameses II. manipulated the clay in the same manner as his descendant of to-day, and he doubtless knew the necessary proportions of clay and sifted ashes for making his composition. [Illustration: ANCIENT VASES, CUPS, AND WATER-JARS.] The boys had already observed the porous character of the Egyptian water-bottle. It allows the water to pass through so freely that the outside is constantly wet; in the dry air of Egypt this outside water evaporates rapidly, and every student of natural philosophy knows that evaporation produces coolness. Especially is this the case if the bottle is placed where there is a current of air, as the evaporation is greatly increased by the action of the wind. One day the boys made an experiment with one of these bottles with the following result: The temperature of the air was 81° Fahrenheit, and so was that of the water with which the bottle was filled. It was hung in a shady place, where there was a good draught, and in half an hour a thermometer lowered into the bottle showed that the water had fallen to 63°, or eighteen less than the surrounding temperature. This process, or a similar one, is in use in all hot countries. Doctor Bronson told the youths that he had seen bottles very like the Egyptian ones in Mexico and South America. In some cases, where the material was not porous, the coolness was produced by wrapping a piece of cloth around a bottle, and keeping it constantly wet while hanging in a current of air. [Illustration: DATE-PALMS, NEAR KENEH.] Another feature of Keneh that attracted attention was the remarkably fine dates that were offered for sale. The dates of Keneh have an excellent reputation in the markets of Cairo and Alexandria, and generally bring a high price. They are not pressed into a solid mass, like most of the dates sold in America, but each one is separate from the others, and only the best are selected for packing. Our friends bought several boxes of these dates, and kept them in their rooms on the steamboat with the intention of taking them to Cairo; but, like many other good intentions, their scheme fell through, as the sweetness and delicate flavor of the contents of the boxes were temptations that could not be resisted. Continual dropping is said to wear away stone, and Fred remarked that continual nibbling would wear away the best box of dates ever known.