The ship was then tested with one screw working ahead and the other astern. One circle was made in 3 minutes 39 seconds, and another in 3 minutes 49 seconds; “in making these circles the action of the ship’s hull was extraordinary, the central part being stationary, and both ends moving round equally. The circle was made on a pivot from the ship’s midship section. The vessel was then put in a straight course, stopped, and from a state of rest the engines were started, one ahead and the other astern, the circle being completed in 3 minutes 55 seconds and the diameter being as before within the ship’s length.”[98] The _Flora_ proved herself faster than any other steamer of her size and horse-power, and became, thanks to her speed, one of the most successful blockade-runners during the American Civil War. [98] _Illustrated London News_, November 29, 1862. [Illustration: H.M.S. “MINOTAUR.”] The experiments in the _Flora_, and afterwards in the _Hebe_ and _Kate_, which were of about the same dimensions and power, were considered so satisfactory that a trial on a larger and more important scale was made in the summer of 1863 with the _Aurora_. This was an iron vessel, 165 feet in length, with a beam of 23 feet, and a depth of 13 feet 6 inches. Her engines, of 120 collective nominal horse-power, drove two three-bladed screws, each independently of the other; the screws were 7 feet in diameter and had a pitch of 14 feet 6 inches. The cylinders were of 26 inches in diameter with a stroke of 21 inches. On her trials she steered equally well with either propellers or rudder, and in the matter of speed passed everything she came across, including the _Sea Swallow_, one of the fastest paddle-boats on the Thames. The distance from Tilbury to the Nore, twenty nautical miles, was done in 1 hour 17 minutes, “an almost unparalleled rate of speed, considering the vessel’s horse-power of engine and hull displacement.”[99] [99] _Times_, August 1863. The _Experiment_ was the first twin-screw boat built for the Navy. The engines were direct-acting, horizontal, high-pressure, and drove two three-bladed propellers, having a diameter of 3 feet 6 inches. She was built by Dudgeon in February 1863.