On the Bahama banks and in the Gulf of Mexico the sponges grow in water of small depth. The fishermen—Spanish, American, and English—sink a long mast or perch into the water moored near the boat, down which they drop upon the sponges; by this means they are easily gathered. The fine, soft Syrian sponge is distinguished by its lightness, its fine flaxen colour, its form, which is that of a cup, its surface convex, voluted, pierced by innumerable small orifices, the concave part of which presents canals of much greater diameter, which are prolonged to the exterior surface in such a manner that the summit is nearly always pierced throughout in many places. This sponge is sometimes blanched by the aid of caustic alkalies; but this preparation not only helps to destroy its texture, but also changes its colour. This sponge is specially employed for the toilet, and its price is high. Specimens which are round‐shaped, large, and soft, sometimes produce very large prices. There are many other varieties known to the commercial world. CHAPTER VII. DAVY JONES’S LOCKER, AND THOSE WHO DIVE INTO IT. Scientific Diving—General Principles—William Phipps and the Treasure Ship—Founder of the House of Mulgrave—Halley’s Wooden Diving‐bell and Air Barrels—Smeaton’s Improvements—Spalding’s Death—Operations at Plymouth Breakwater—The Diver’s Life—“Lower away!”—The Diving‐_Belle_ and her Letter from Below—Operations at the Bottom—Brunel and the Thames Tunnel—The Diving Dress—Suffocation—Remarkable Case of Salvage—The “Submarine Hydrostat”—John Gann of Whitstable—Dollar Row—Various Anecdotes—Combat at the Bottom of the Sea—A Mermaid Story—Run down by the _Queen of Scotland_. The art of unassisted diving having been considered, the reader’s attention is invited to divers and diving aided by scientific appliances. But for these developments, how could one hope to recover anything large or valuable that had once disappeared beneath the waves? How properly build gigantic breakwaters, piers, and bridges, or examine and clear choked ports and channels?(29) Some of the grandest achievements of modern practical science would have been impossible without their aid.