SECTION X. 
OF STEAM NAVIGATION. 
593. On the value of the application of steam to impel vessels, it has become 
unnecessary to say more than that its employment is extending rapidly at almost 
every place on the globe where the trade is considerable, and that its use is limited 
only by its yet imperfect state. If we had intended to have confined our researches 
to the mere application of an engine to a vessel already constructed, our labour 
would have been short, and easily completed: but the construction of vessels is 
a subject which is capable of improvement; and while we think there is a power 
in science to indicate the steps by which it may be improved, it is our duty to 
submit it to the reader. 
The forms of vessels for stability, speed, capacity, and strength; the kinds of 
vessels for different purposes, the resistance, and modes of propulsion; the nature 
of the engines adapted for vessels, the strength of their parts, and the species of 
fuel, and its management to obtain the best effect; are all objects of importance, 
and each of these we propose to consider. 
These inquiries are equally applicable to mercantile and to government pur 
poses, but there is yet another portion of the subject to which it would be desirable 
to direct attention. 
In the case of war, steam boats will become a means of attack; therefore it ought 
to be considered how far they may become a means of defence, the power of 
resisting being the best guard against a mode of attack, which will deprive us of 
many of the advantages of our insular state. Hence, the construction of gun boats 
for the defence of rivers, and of river navigation, and harbours, would be a proper 
subject for inquiry, if our limits did not forbid it. 
Of the Forms of Vessels for Stability, Speed, Capacity, and Strength. 
594. In considering the properties of a vessel, the orderly arrangement of our 
subject requires that we should treat,—First, Of stability, or the power a vessel