The upper portion of the compound vessel consisted of decks and quarters for passengers and crew and holds for freight. These were all comprised within a vast upper hull, which rested upon the lower hull containing the motive power, the only point of contact being an enormous ball-and-socket joint. Thus, no matter how much the lower hull might roll and pitch and toss, the upper hull remained level and comparatively undisturbed. Not only were comfort to passengers and security to movable freight gained by this arrangement of the compound vessel, but it was now possible to build the lower hull of much less size than had been the custom in the former days of steamships, when the hull had to be large enough to contain everything. As the more modern hull held nothing but the machinery, it was small in comparison with the superincumbent upper hull, and thus the force of the engine, once needed to propel a vast mass through the resisting medium of the ocean, was now employed upon a comparatively small hull, the great body of the vessel meeting with no resistance except that of the air. It was not necessary that the two parts of these compound vessels should always be the same. The upper hulls belonging to one of the transatlantic lines were generally so constructed that they could be adjusted to any one of their lower or motive-power hulls. Each hull had a name of its own, and so the combination name of the entire vessel was frequently changed. It was not three o'clock when the Euterpe-Thalia passed through the Narrows and moved slowly towards her pier on the Long Island side of the city. The quarantine officers, who had accompanied the vessel on her voyage, had dropped their report in the official tug which had met the vessel on her entrance into the harbor, and as the old custom-house annoyances had long since been abolished, most of the passengers were prepared for a speedy landing. One of these passengers--a man about thirty-five--stood looking out over the stern of the vessel instead of gazing, as were most of his companions, towards the city which they were approaching. He looked out over the harbor, under the great bridge gently spanning the distance between the western end of Long Island and the New Jersey shore--its central pier resting where once lay the old Battery--and so he gazed over the river, and over the houses stretching far to the west, as if his eyes could catch some signs of the country far beyond. This was Roland Clewe, the hero of our story, who had been studying and experimenting for the past year in the scientific schools and workshops of Germany. It was towards his own laboratory and his own workshops, which lay out in the country far beyond the wide line of buildings and settlements which line the western bank of the Hudson, that his heart went out and his eyes vainly strove to follow.