his twin
wolf-nursling, but it is the plough of Bocchi Gaetano of Parma, is
twelve feet long and weighs something under half a ton. Another, hard
by, is two feet longer and has but one handle. Efforts are evident,
however, to assimilate the country to the portions of Europe more
advanced in mechanical matters. When we reflect upon how much we owe to
Italy, we can but wish her well, but we cannot delay long with her in a
search for objects of mechanical interest except to examine her models
of tunnels, manner of scaffolding, boring and blasting. The Mont Cenis
tunnel must stand as the grandest work of its kind until that of Saint
Gothard is finished. An exemplification by a model constructed to a
scale of the electric ballista of Spezzia for testing the hundred-ton
gun lately made in England for Italy attracts a great many visitors, and
the large photographs which give the condition of the butt after each
impact of the projectiles brings up again the double problem as it is
stated: How to construct a gun and projectile which shall be able to
pierce the heaviest armor; and how to construct armor which shall be
proof against the heaviest shot. Many saw with interest in the Machinery
Building at the Centennial the eight-inch armor-plating made by Cammell
of Sheffield, tested in one case by nine spherical shots overlapping,
making an indentation of 3.12 inches with balls from a seven-inch gun
driven by thirty pounds of powder at a range of seventy feet. They are
here again, and so is the nine-inch armor with a much deeper indentation
from a chilled Palisser bolt. Here is also a new-comer, John Brown,
whose armor of four and a half inches of steel welded on to the same
thickness of iron resists the Palisser bolt, which only penetrates the
thickness of the steel. What might happen to it with a pointed steel
bolt from a sixty- or one-hundred-ton gun is another matter. To set our
minds at rest as to what would occur in the event supposed comes Sir
Joseph Whitworth, who exhibits his gun with polygonal rifling, the bore
being a hexagon with rounded corners. The projectiles are moulded of the
same shape, and are fired as they are cast, without planing. One of
these bolts, six diameters long and weighing twenty-nine and a half
pounds, was fired from a twelve-pounder gun through a four and a half
inch armor-plate. The exhibit also shows a flat-fronted Whitworth
fluid-pressed steel shell, three diameters long, weighing eight hundred
a