About midway between Haïfa and Acre, the traveler, pausing at some resting-place in the progress of his ascent, may trace the course of the river Belus, as it meanders through the plain beneath him, northwardly, toward an outlet just in the rear of Acre, where it empties into the sea. The course and direction of the stream are delineated upon the map near the commencement of this article. This river is celebrated as the place where, according to ancient story, the discovery of the art of making glass was first made by means of an accidental vitrification which chanced to take place under certain peculiar circumstances, on its shores.[4] Glass is composed essentially of silicious substances--such as sand--combined with certain alkalies by fusion. For sand, though very refractory if exposed alone to the influence of heat, when mixed with these alkaline substances fuses easily, and _vitrifies_, that is it forms a glass, which is more or less perfect according to the precise nature of the substances employed, and the arrangements of the process. The story of the origin of the discovery is, that a vessel came into the mouth of the Belus from the Bay of Acre, laden with certain fossil alkalies which were found somewhere along the coast, and were used in those times for certain purposes, and that the sailors landed on the beach and built a fire there, with a view of taking supper on the shore. When the fire was made they looked about the beach for stones to use as a support for their kettle; but the soil being alluvial and sandy they were not able to find any stones, and so they brought instead three fragments of the alkaline fossil, whatever it might have been, with which their vessel was loaded. These fragments they placed in the margin of the fire which they had built upon the sand, and rested the kettle upon them; thus by means of the alkali, the sand, the metal, and the fire, all the conditions were combined that are essential to produce a vitrification, and after their supper was ended the seamen found the glassy substance which had been produced, lying beneath the fire. They made their discovery known, and the experiment was repeated. Soon after this the regular manufacture of glass for vessels and ornaments was commenced in the city of Sidon, which lies on the coast of the Mediterranean, not many miles north of the mouth of the Belus, and from Sidon the art soon spread into every part of the civilized world. [Illustration: THE DISCOVERY OF GLASS.] THE CONVENT.