Although the _Mauretania_ and _Lusitania_ are usually spoken of as sisters, there are some differences in the design. They are the same length, but the former is six inches deeper, which adds about 500 tons to her registered tonnage. Special high tensile steel was used to a greater extent in the construction of the _Mauretania_, making that vessel something like 1000 tons lighter. Her lines are slightly finer, and it has been claimed to account for her speed that there is some superiority in her engines. In regard to the structure of the _Lusitania_, it is stated that with the whole structure of mild steel Lloyd’s accepted a stress of ten tons to the square inch, and that in view of the strains thrown upon the upper works a high tensile steel of less scantling was adopted for those parts; a material having been discovered with a tensile strength 20 per cent. greater than mild steel, a reduction of 6 per cent. in the scantlings was allowed from those for mild steel. The Cunarders were not the first vessels by many years in which high tensile steel of a strength of thirty-six tons was used, as it was introduced twenty-three years ago in the steam-ship _America_. Whether the great Cunarders pay in the financial sense is known only to the management of the line, but there is no denying that they are a great national asset. A detailed estimate, published at the time they were about to make their first voyages, placed the expenditure at £17,990 per voyage, and the income, allowing for a full passenger list, at £31,350.[91] But this did not profess to be more than a general estimate and in no sense official. The question has been raised in various quarters whether an equal speed could not have been obtained from reciprocating engines with a less consumption of coal; as a reply to this view it has been pointed out that the sizes that would have been required for the ingots, &c., for the machinery were beyond the capabilities of our steel manufacturers, and thus, as so often has happened, the new set of conditions was met by the new development of invention. [91] _Liverpool Courier_, November 18, 1907. KAISER CAMPANIA. OCEANIC. BALTIC. WILHELM II. LUSITANIA.