Although it was intended to render the experiments final and conclusive as a practical demonstration under service conditions of the destructive effects of the Whitehead torpedo when directed against a modern vessel of war, the results still leave behind them much uncertainty.  The Resistance was built of iron, whereas battle ships are now exclusively constructed of steel, and it would be perhaps hazardous to state that the behavior of the two metals under a sudden and violent shock would be exactly the same.  The construction of the double bottom of the old ship is also different.  Since the last experiments were carried out against her, however, measures have been taken to make her as far as possible the counterpart, so far as under water arrangements and coal protection are concerned, of a modern ship of war.

At the last attack, the Whitehead was directed against the after part of the hull on the port side in wake of the boilers.  During the present series of experiments the old ship was assailed on the same side, but directly amidships, in the neighborhood of the engine room.  As no steam was got up in the boilers, the effect of the jar upon the steam pipes, glands, and feed connections remains a matter of speculation.  So far as the consequences of the burst upon the structure of the hull itself is concerned, every care was taken to make the ordeal as complete and instructive as possible.  The wing passage, which has a maximum diameter of 3 ft. diminishing to a point, was left empty, although at the former experiments the lower portions were filled with coal.  But behind this, and at a distance of 8 ft. from the bulkhead, a longitudinal or fore and aft steel bulkhead 3/8 in. thick had been worked to a length of 61 ft., and, with the coal with which the intervening compartment was packed, formed (as in recent armorclads) a solid rampart, 20 ft. high, for the defense of the engine room.

The height of the double bottom between the outer and inner skin plating is 21/2 ft.  The watertight compartments were divided into stations by means of vertical lightening plates pierced by three holes, and in order to make them, as far as was practicable, resemble the bracket frames of a modern armorclad, the center of the plates was cut away so as to leave a single oval hole instead of the three circular holes.  In view of the differences of opinion which exist on the part of experts on the subject of under water protection, the officers of the Vernon had determined to submit the problem to the test of experiment.  For this purpose steel armor 11/2 in. thick had been worked along the outside of the upper skin of the double bottom throughout one of the compartments, in addition to the other protection mentioned.  The Resistance had been brought down by iron ballast to a trim of 25 feet 9 in. aft and 19 ft. 7 in. forward, giving a mean draught of 22 feet 8 inches.  She was consequently rather further down by the stern than before, but was in other respects the same.