Lady Olivia thanked the professor for his explanation, and murmured an additional word or two of admiration for the wonderful armour; whereupon von Schalckenberg--perceiving perhaps that her ladyship's interest in what was really one of his masterpieces of ingenuity was not, after all, particularly keen--opened a door opposite the one by which they had entered the diving-room, disclosing a small vestibule from which sprang a spiral staircase made of the same beautiful white metal that was everywhere to be met with on board this marvellous ship. Leading the way round past the foot of the staircase, the professor halted before a door inscribed with the words "Engine-Room." This door he threw open, and, as before, with a profound bow, motioned Lady Elphinstone to enter. The first emotion of those who entered this important compartment for the first time was invariably one of disappointment; for the room, although full of machinery, was small-- disproportionately so, it appeared, compared with the bulk of the ship and the power required to drive it at the enormous speeds that had been indisputably attained by the _Flying Fish_. And this emotion was further increased by contemplation of the machinery by means of which these high speeds had been attained. The main engines, consisting of a set of three-cylinder compound engines, constructed throughout of polished aethereum, and consequently presenting an exceedingly handsome appearance, suggested rather the idea of an exquisite large-sized model in silver than anything else, the set occupying very little more space than those of one of the larger Thames river steamers. But the impression of diminutiveness and inadequacy of power merged into one of astonishment nearly approaching incredulity when the professor casually mentioned that the vapour by which the engines were driven entered the high-pressure cylinder at the astounding pressure of five thousand pounds to the square inch, and that, although the engines themselves made only fifty revolutions per minute, the main shaft, to which the propeller was attached, made, by means of speed-multiplying gear, no fewer than one thousand revolutions per minute in air of ordinary atmospheric pressure!