he described the modern British battleship as a "spoiled Trafalgar." There was perhaps some reason in what he said.--_The Engineer._ * * * * * DEMOLITION OF ROCKS UNDER WATER WITHOUT EXPLOSIVES-LOBNITZ SYSTEM.[1] [Footnote 1: Read before the Engineer's Club, Philadelphia. Translated from _Nouvelles Anodes de la Construction,_ March, 1890.] By EDWIN S. CRAWLEY. The methods of demolishing rocks by the use of explosives are always attended by a certain amount of danger, while at the same time there is always more or less uncertainty in regard to the final result of the operation. Especially is this the case when the work must be carried on without interrupting navigation and in the vicinity of constructions that may receive injury from the explosions. Such were the conditions imposed in enlarging the Suez Canal in certain parts where the ordinary dredges could not be used. Mr. Henry Lobnitz, engineer at Renfrew, has contrived a new method of procedure, designed for the purpose of enlarging and deepening the canal in those parts between the Bitter Lakes and Suez, where it runs over a rocky bed. It was necessary to execute the work without interrupting or obstructing traffic on the canal. The principle of the system consists in producing a shattering of the rock by the action of a heavy mass let fall from a convenient height, and acting like a projectile of artillery upon the wall of a fortress. From experiments made in the quarry of Craigmiller, near Edinburgh, with a weight of two tons shod with a steel point, it was found that with a fall of about 5.5 meters (18.04 ft.) there was broken up on an average more than 0.113 cubic meter (0.148 cubic yard) of hard rock per blow. The first blow, delivered 90 centimeters (2 ft. 111/2 in.) from the wall face, produced an almost imperceptible rent, a second or a third blow applied at the same place extended this opening often to a length of 1.50 meters (4 ft. 11 in.) and to a depth of from 90 to 120 centimeters (2 ft. 11 in. to 3 ft. 11 in.) The next blow opened the fissure and detached the block of rock. The application of the same system under water upon an unknown surface would obviously modify the conditions of the experiment. Nevertheless, the results obtained with the "Derocheuse," the first dredging machine constructed upon this principle, have realized the hopes of the inventor.