In attacking in front, the vertical tube is laid over till it is parallel to the water surface, and the horizontal tube is allowed to incline sufficiently far to allow of the end of the pole, when run out, to be depressed from 8 to 10 feet below the water-line. It is held in this position by a pair of blocks attached to the top of a short mast. In attacking on the broadside, the vertical tube is laid over till it assumes a position such as to allow of the pole, when swung round, to touch an enemy's vessel at about 8 or 10 feet below the water line. The speed trials of the Austrian boat took place on the 11th of September, 1875, when she did 24,700 revolutions on her hour's run on the Thames, and the number of revolutions required to do a knot in still water was found to be 1357. This gives the distance run in the hour as 18·202 knots, or 3·202 knots over the contract speed. The steam pressure averaged 105 lbs. per square inch, and the vacuum 25-1/2 inches during the run. In the case of the French boats, the total number of revolutions done in the two hours' run in the roadstead off Cherbourg was 49,818, and the number required to do a knot in still water was found to be 1382, so that the distance run in the two hours was 36·05 knots, or just over the contract speed. During the two hours, the average steam pressure was 108 lbs. per square inch, and the vacuum 25 inches. The Austrian boat was sent to her destination on board a steamer, but the French boats, under the command of an experienced captain, steamed by themselves from Chiswick to Cherbourg, not crossing at the nearest points and running along the shore, but going boldly from Dover direct to Cherbourg. Shortly after the arrival of the French boats in Cherbourg, they were altered so as to attack in front only, as the French authorities found that these small vessels were better adapted for resisting the effects of an explosion at the bow than at any other part. The arrangement adopted is shown at Fig. 152, and consisted of a steel pole about 40 feet in length, having one end about 6 inches diameter, and solid, and the other about 1-1/2 inches diameter, and hollow; this pole was mounted at its solid end on small pulleys, which ran upon two ropes stretched fore and aft of the vessel; the other end, to which the torpedo was attached, was led over a pulley fixed on the bow. Ropes passing over pulleys to a windlass in the after compartment were attached to the inboard end, and by turning the windlass the pole was drawn backwards or forwards as required. It will be observed that as the pole is drawn forward, the inboard end being constrained to move in a line parallel to the deck, the outer end is depressed in the water, and is so adjusted that when the pole is run out to its full extremity, the torpedo is depressed to about 8-1/2 feet below the water level.