After this failure (which, however, was admitted to be one of accident and not of principle) the government did not consider itself justified in bestowing further time or incurring greater expense in trying this engine. Mr. Howard, however, has himself built a new vessel, in which he is about to place a pair of forty-horse engines. This vessel is now (December, 1835) nearly ready, and will bring the question to issue by a fair experiment. The advantages of the contrivance as enumerated by the patentee are:--
_First_, The small space and weight occupied by the machinery, arising from the absence of a boiler.
_Secondly_, The diminished consumption of fuel.
_Thirdly_, The reduced size of the flues.
_Fourthly_, The removal of the injurious effects arising from deposite and incrustation.
Some of these improvements, if realized, will be attended with important advantages in steam navigation. Steamers of a given tonnage and power will have more disposable space for lading and fuel, and in short voyages may carry greater freight, or an increased number of passengers; or by taking a larger quantity of fuel,[37] may make greater runs than are now attainable; or, finally, with the same tonnage and the same lading, they may be supplied with more powerful machinery.
[Footnote 37: The fuel used in this form of engine is coke, and not coal. A ton of coke occupies the same space as two tons of coal; the saving of tonnage, therefore, by the increased economy of fuel will not be in so great a proportion as the saving of fuel. A quantity of fuel of equivalent power will occupy about half the present space, but the displacement or immersion which it produces will be only one fourth of its present effect.]
(117.) To obtain from the moving power its full amount of mechanical effect in propelling the vessel, it would be necessary that its force should propel, by constantly acting against the water in a horizontal direction, and with a motion contrary to the course of the vessel. No system of mechanical propellers has, however, yet been contrived capable of perfectly attaining this end. Patents have been granted for many ingenious mechanical combinations to impart to the propelling surfaces such angles as appeared to the respective contrivers most advantageous. In most of these, however, the mechanical complexity has formed a fatal objection. No part of the machinery of a steam vessel is so liable to become deranged at sea as the paddle-wheels; and, therefore, such simplicity of construction as is compatible with those repairs which are possible on such emergencies is quite essential for safe practical use.