This shell might contain explosives or not, as might be considered desirable, and it was not intended to fire it from a cannon, but to start it on its course from a long semi-cylindrical trough, which would be used simply to give it the desired direction.

After it had been started by a ram worked by an engine at the rear end of the trough, it immediately bean to propel itself by means of the mechanism contained within it.
But the great value of this shell lay in the fact that the moment it encountered a solid substance or obstruction of any kind its propelling power became increased.

The rings which formed the cone on its forward end were pressed together, the electric motive power was increased in proportion to the pressure, and thus the greater the resistance to this projectile the greater became its velocity and power of progression, and its onward course continued until its self-containing force had been exhausted.
The power of explosives had reached, at this period, to so high a point that it was unnecessary to devise any increase in their enormous energy, and the only problems before the students of artillery practice related to methods of getting their projectiles to the points desired.

Progress in this branch of the science had proceeded so far that an attack upon a fortified port by armored vessels was now considered as a thing of the past; and although there had been no naval wars of late years, it was believed that never again would there be a combat between vessels of iron or steel.
The recently invented magnetic shell made artillery practice against all vessels of iron a mere mechanical process, demanding no skill whatever.
When one of these magnetic shells was thrown anywhere in the vicinity of an iron ship, the powerful magnetism developed within it instantly attracted it to the vessel, which was destroyed by the ensuing contact and explosion.

Two ironclads meeting on the ocean need each to fire but one shell to be both destroyed.