The finest sponges come from Tripoli, and along the shores of the Mediterranean, the possessions of Turkey being the best field, the Spanish, French, and Italian coasts being, strange to say, devoid of them. The coarser kinds of sponges are found in the West Indies and off the Florida coast, none of the finest grade existing in American waters. The average value of Florida sponges is 80 cents a pound, while those from the Turkey coast are often worth as much as $50 a pound. There are many sponge beds along the coast of Florida, at well-protected places fenced in with natural fortifications and dams. They are carefully watched until reaching maturity, and are finer than those living wild in the sea. After three years the sponges are ready for harvest. The choicest then, the full-grown ones, are pulled up, the others being left to reproduce until of larger size. Every year the value of a sponge farm increases, and enormous crops are yielded. It is easy to gather sponges here, for the water is clear and they are easily raised with a pole or tongs. It is not so in Tripoli, however. There the work has to be done by divers, and as the fisheries have been so well worked, it is necessary for the divers to go deeper and deeper for them every year. Only the most desperate men are willing to undertake the task, notwithstanding they are paid ten times the usual wage paid to men in that country. Out of 600 divers employed, 150 to 200 die each season, either from asphyxiation, paralysis, or cuts from their knives. The diver in Tripoli seldom has diving-bells or suits such as are used in Europe and America. He goes down into the ocean, sometimes to the depth of 100 fathoms, taking with him a flat piece of stone of a triangular shape, with a hole drilled through one of its corners. A cord from the boat is attached to this stone and he uses it to guide him. Upon reaching the growing sponges he tears them off the rocks or cuts them with a sharp knife, places them under his arms, and then pulls at the rope, which gives the signal to the men in the boat to haul him up. The work is said to be done not so well by means of a diving-bell, the utmost care being necessary that the delicate organisms should not be torn. Sponges obtained by dragging are torn and sell for low prices. Those secured at such risk are the best and are used by surgeons in delicate operations. They do not grow as rapidly in the Mediterranean as in our water, an ordinary bath sponge, measuring about a foot in diameter, being ten years old.--_E. K. M._ COMMON MINERALS AND VALUABLE ORES. IV.--COPPER AND LEAD ORES. THEO. F. BROOKINS, B. S.