Captain Ericsson, a Swedish army officer who had come to London and established himself as a civil engineer, had a contemporary success with a boat fitted with two large-bladed propellers each 5 feet 3 inches in diameter. So successful was he, indeed, that he invited the Board of Admiralty to take a trip in tow of his novel craft; a trip which had important and unexpected results on the subsequent progress of steam navigation. One summer day in ’37 the Admiralty barge, in which were the Surveyor and three other members of the Board, was towed by Ericsson’s screw steamer from Somerset House to Limehouse and back at a speed of 10 knots. The demonstration was a complete success, and the inventor anticipated some further patronage of his invention. But to his chagrin nothing was asked of him, and to his amazement he was subsequently informed that the proposal to propel warships by means of a screw had been pronounced impracticable. Never, perhaps, in the whole history of mechanical progress has so signally wrong a decision been made, never has expert opinion been so mistaken. Engineers and shipbuilders all failed to realize the possibilities of the screw. The naval authorities who, in the face of their personal experience, dismissed the project as impracticable (owing to some anticipated difficulties in steering ships fitted with screws) merely expressed the unanimous opinion of the time. “The engineering corps of the empire were arrayed in opposition to it, alleging that it was constructed on erroneous principles, and full of practical defects, and regarding its failure as too certain to authorize any speculations even of its success. The plan was specially submitted to many distinguished engineers, and was publicly discussed in the scientific journals; and there was no one but the inventor who refused to acquiesce in the truth of the numerous demonstrations, proving the vast loss of mechanical power which must attend this proposed substitute for the old-fashioned paddlewheel.”[154] Yet in five years’ time steamers designed for paddlewheels were being converted to carry screws, and a great screw-propelled liner, the _Great Britain_, had been launched for the Atlantic traffic!