following is an illustration, was, certainly, in advance of any other at that time, and is, I believe, still considered the best and most useful type. In the account of it furnished by its able and ingenious inventor, it is said to be the “only propelling instrument of any description which has the peculiar and inherent property of acting with an increased impulse against the water from the leading part, first taking its action against the water to the end, however long or short such propeller may be upon its axis.” [Illustration] However, be that as it may, when an impartial review is taken of all the facts, it may be said of Messrs. Woodcroft, Ericsson and Smith that, while each may be regarded as the individual author of their respective plans, conceiving as they did their designs apart from each other, we are indebted to them conjointly for this most valuable invention. While the relative merits of the paddle-wheel and screw were being tested, the attention of scientific men was necessarily directed to the different forms of ships or lines best adapted to the various requirements of maritime commerce, which the introduction of steam had either created or materially developed. Vessels of every conceivable form, and of varied dimensions, have been in use from the earliest ages: we have had, of one sort or another, canoes, coracles, barges and yachts, coasters and Indiamen, with frigates and line-of-battle ships such as they were, almost from the dawn of history, and no doubt their owners and builders bestowed much thought and exercised considerable skill in their construction, so as to suit the varied purposes for which they were required; but it is only within our own time that a thorough scientific knowledge has been invited to aid in the construction of our merchant ships. That knowledge has become much more necessary now than it ever was before. To construct an useful and first-class steam-vessel, we must first build a hull adapted to receive machinery, and then erect suitable engines and boilers with an appropriate propelling apparatus, combining the whole into a form such as will insure safety and speed, the requisite space for the crew, machinery, fuel, and stores, with accommodation for passengers and their numerous wants, and, also, sufficient space for a remunerative cargo. [Sidenote: In building fit vessels, the trade in which they are to be employed must be considered.]