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MARINE REVIEW. aVOL. V:. CLEVELAND, OHIO, THURSDAY, MARCH 24. 1892. Nori Gunboat Petrel, United States Navy. The accompanying illustration of the United States gunboat Petrel is from the Railroad and Engineering Journal of New York. "While of course not equal in weight of fighting power to the larger cruisers" says the Journal, "this ship is one of a class which is very useful on several of the foreign stations and very efficient. In case of war these vessels might prove excellent auxiliaries to the larger boats. 'The Petrel was built under con- tract by the Columbia Iron Works in Baltimore. 'The contract was let in December, 1886, and the vessel was finally accepted by the navy department in October, 1889. Since then she has been in commission in service of different kinds, and is now on her way to join the China squadron, for service in which she is particularly adapted. The general dimensions of this vessel are : Length between perpendiculars, 175 feet; beam, 31 feet; depth of hold, 15 feet 7 inches; mean draft, 11 feet 7 inches; displacement, 870 tons. She has three masts, with a barkentine rig, and a considerable spread of canvas. The hull is of steel, and is, divided by nine transverse water-tight bulkheads. The engine and boiler space is surrounded and covered as completely as possible by the coal bunkers, which are divided into compartments, which can be separately flooded and drained. Further protection is afforded by a steel deck three-eighths of an inch thick, which curves from a height of 8 inches above the water-line at the crown to 2 feet 6 inches bélow at the sides. ; The armament consists of four 6-inch breech-loading guns mounted in sponsons, two on each side, at a height of ro feet 8 inches above the water-line, and fitted with segmental steel shields. The secondary battery includes two 6-pounder rapid-fire guns, and two revolving cannon. 'The armament is a heavy one for a ship of this size. The Petrel is propelled by a single screw; it is three-bladed, 9 feet 9 inches in diameter, with a mean pitch of 12 feet 3 inches. The screw is driven by a two-cylinder horizontal compound en- gine, with cylinders 25 inches and 46 inches in diameter and 33 stroke. Steam is furnished by two cylindrical boilers 8 feet 8 inches in diameter and 18 teet 41% inches long. 'The total grate ee ee area is 83.2 square feet, and the heating surface 2,796 square feet. On a four-hour's trial trip, with 89 pounds pressure in the boilers, the engines developed an average of 1,095 horse power and the average speed was 11.8 knots. Under forced draft the maximum power developed was 1,513 horse power. ~--~Machinery of the Steamer John J. Hill. In the elegant supplemental engravings accompanying this issue the engines and boiler of the steamer John J. Hill, a vessel built on the lakes for coast service, are represented. They were built by the Dry Dock Engine Works of Detroit, which is opera- ted in conjunction with the Detroit Dry Dock Company. The boat is 178 feet long, 40 feet beam and 17 feet hold. The en- gines are fore and aft compound, 20 and 40 inches by 36 inches stroke. The boiler is 9 feet in diameter and 14 feet long, al- lowed 110 pounds pressure, and the boat in all her parts is built after the United States standard rules,