In proportion as the capacity of the vessel is increased, in the same ratio or nearly so must the mechanical power of the engines be enlarged, and the consumption of fuel augmented.... It is therefore demonstrable that, in the present state of steam navigation, if this voyage shall be accomplished in one uninterrupted trip, the vessel which performs it must, whatever may be her power and tonnage, be capable of extracting from coals a greater mechanical virtue, in the proportion of three to two, than can be obtained from them by the combined nautical and mechanical skill of Mr. Lang, the builder of the ‘Medea,’ and Messrs. Maudslay and Field.... That the passage from Liverpool to New York cannot on any occasion be made in one run by a steam-ship we do not maintain.... The average time of the outward voyage to New York is thirty-six days, and we say that when the circumstances of wind and water are such that a sailing vessel would require that time to make the passage, a steamer cannot make it without an intermediate supply of fuel. (Pp. 127, 139, 143.) To sum up Dr. Lardner’s views in his own words written at about this time,[122] ‘We have as an extreme limit of a steamer’s practicable voyage, without receiving a relay of coals, a run of about 2,000 miles.’[123] It will be seen from these extracts that the proposition Dr. Lardner laid down as the basis of his ‘demonstration’ was, that the power of the engines must be increased as the size of the vessel. Were this true his conclusion would also be true--namely, that the capacity of a given vessel regularly to accomplish a given voyage does not increase with the increase of size, since the consumption of fuel is augmented in about the same ratio. This assumption is directly opposed to the opinion held by Mr. Brunel, and acted on by him in his recommendations to the Steam-Ship Company--namely, that while the tonnage of a ship is increased as the cube of her dimensions, the resistance is increased only about as the square. This question was the main point at issue between Dr. Lardner and Mr. Brunel; and the proposition which Mr. Brunel then asserted is at the present time the basis of the calculations which determine the proportion between the tonnage of a steam-ship and the length of voyage she has to perform without a relay of fuel. * * * * * The history of the ‘Great Western’ steam-ship has been interrupted by this examination of Dr. Lardner’s propositions. The weight at one time attached to his opinions, the sinister influence they exercised over the early efforts of those who differed from him, and the great and enduring importance of the points at issue, have made it necessary to refer to them at length.