362 Rev. W. Ritchie on impelling Steam Vessels. \[Nov. 
In the application of steam to the impelling of boats and other 
vessels, the following requisites seem still wanting: In the first 
place, to apply the whole force in the direction in which the 
vessel moves, and in such a manner as not to increase the 
breadth of the vessel, which greatly retards its velocity. In 
the second place, to apply it in such a manner as not to inter- 
rupt the motion when it is found advantageous to employ sails 
either with or without the assistance of steam. And lastly, to 
arrange the moving power in such a manner as not to injure the 
sides of canals. In considering this important subject, the fol- 
lowing method occurred to me, which appears at least worthy of 
the attention of those who are engaged in building steam vessels. 
Instead of circular motion, let a horizontal motion be communi- 
cated to two rods passing through circular apertures in the stern 
of the vessel. To the end of each of these rods, two metallic 
plates of a convenient size are to be fixed, having their planes 
at right angles to the horizon, and moveable about strong well- 
polished joints. When the plates are shut, they form a small 
angle with one another, and when opened to their utmost 
extent, they form about a right angie. When the rods are 
pushed suddenly out, the valves open and present a large surface 
to the reaction of the water, which will evidently push the ves- 
sel in the opposite direction ; when the rod is drawn back, the 
valves shut, and present only a small surface to retard the 
motion of the vessel. 
Not satisfied with reasoning alone, I had recourse to actual 
experiment. Having procured a long pole, I attached to one 
end of it a pair of valves similar to what I have described, and 
endeavoured to impel a boat by the strength of aman. The 
success of the experiment exceeded my most sanguine expecta- 
tions. We moved witha velocity nearly equal to what could be 
produced by a man with a pair of oars, and it appeared obvious, 
that with a little practice, and a pair of such valves, the velocity 
could be greatly increased; but whether a similar effect could 
be produced on a large scale, is a question which cannot well 
be solved by calculation. Experiment alone must determine the 
ont. 
Should this mode be found to answer, a steam boat can be 
constructed with the same external appearance as any other 
vessel. Such a contrivance would be well adapted for boats 
moving on canals. It might also be applied with considerable 
advantage to vessels meeting with calms or contrary winds, 
