Another important limitation which renders it impossible to give a passenger ship the elaborate subdivision of a warship, is the necessity of providing large cargo spaces and wide hatchways for the convenient handling and stowage of the freight, upon which a large proportion of the passenger-carrying vessels chiefly depend for their revenue. [Illustration: Courtesy of _Scientific American_ Longitudinal bulkheads form an inner skin through machinery spaces. Transverse bulkheads extend two decks (20 feet) above water line, the height increasing towards the ends. LONGITUDINAL SECTION AND PLAN OF THE IMPERATOR] On the other hand, the main features of warship protection may be so applied to the large merchant ship as to render her as proof against collision with icebergs, derelicts, or with other vessels, as the warship is against the blow of the ram, the mine, or the torpedo. And the merchant ship of the size of our largest ocean liners has the great advantage over the warship (provided that the average size of her compartments be not too greatly increased) that her great size is in itself a safeguard against sinking. By way of showing what can be done in applying warship principles of subdivision to merchant vessels, we shall consider in some detail three notable ships, the _Mauretania_, the _Kronprinzessin Cecilie_, and the recently launched _Imperator_. The _Mauretania_ and her sister, the _Lusitania_, were built under an agreement with the British Government, who stipulated that they would provide a sum sufficient to pay for the new vessels not to exceed $13,000,000, secured on debentures at 2¾ per cent. interest. The two ships were to be of large size and capable of maintaining a minimum average ocean speed of 24½ knots in moderate weather. The government also agreed that if the ships fulfilled these conditions, the Cunard Company was to be paid annually $750,000.00. In return for this extremely liberal assistance, the Cunard Company agreed to employ them in the British mail-carrying service; to so construct them that they would be available for use as auxiliary cruisers; and to hold them at the instant service of the government in case of war. In addition to holding the ships at the service of the government, it was agreed that all the officers and three-fourths of the crew should be British subjects, and that a large proportion should belong to the Royal Naval Reserve. The ships were thus to be utilised as a training school for officers and seamen, and with this point in view a record of the personnel was to be made each month. The particulars of these two ships as finally constructed are as follows: Length over all 790 feet; beam, 88 feet; displacement, 46,000 tons; and horsepower, 70,000. Both vessels greatly exceeded the contract speed of 24½ knots, the _Lusitania_ having maintained over 25½ knots and the _Mauretania_ 26 knots for the whole run across the Atlantic.