the advantage.  It is impossible, however, to avoid the conviction that the Dupuy de Lome would be a most powerful and disagreeable enemy for either of the eight great ironclads of Great Britain now building to encounter on service.  The Hood and Royal Sovereign have many vulnerable points.  At any position outside of the dark and light colored portions of armor plate indicated in our drawing, they could be hulled with impunity with the lightest weapons.  It is true that gun detachments and ammunition will be secure within the internal “crinolines,” but how about the other men and materiel between decks?  Now, the Dupuy de Lome may be riddled through and through bf a 131/2 in. shell if a Royal Sovereign ever succeeds in catching her; but from lighter weapons her between decks is almost secure.  We cannot help feeling a sneaking admiration for the great French cruising battleship, with her 6,300 tons and 14,000 horse power, giving an easy speed of 20 knots in almost any weather, and protected by a complete 4 in. steel panoply, which will explode the shells of most of our secondary batteries on impact, or prevent their penetration.  In fact, there is little doubt that the interior of the Trafalgar, whether as regards the secondary batteries or the unarmored ends, would be probably found to be a safer and pleasanter situation, in the event of action with a Dupuy de Lome, than either of the naked batteries or the upper works of the Royal Sovereign.  This is what Sir E.J.  Reed was so anxious to point out at the meeting of naval architects in 1889, when 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.