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