VOL. XXXI.] PHILOSOPHICAL TRANSACTIONS. 545 



A Method for rowing Men of War in a Calm. By M. Du Quet. 



N"* 369, p. 239. 



To perfect the art of navigation, two things seem principally wanting, viz. 

 an easy method for finding the longitude at sea, and a way to give a vessel its 

 course in a calm. I flatter myself I have found the last, and hope to make it 

 appear by reason and experiment, that a man of war may make a league an 

 hour in a calm, by means of revolving oars, which are easily applied to the 

 sides of the ship, without occasioning any incumbrance. 



A body floats on water, when it weighs less than the volume of water, whose 

 place it takes up; and it sinks more or less in the water, only in proportion as 

 its volume is more or less increased. A body lying in still water is as it were in 

 equilibrio; the least effort gives it motion, and makes it lose that equilibrium. 

 If the effort be continued, though ever so little, the motion it communicates 

 will be very sensible. How great soever the weight of the body be, when once 

 it is in motion, it will always continue so, if nothing hinders it. 



On these principles, I consider the motion a vessel receives by means of oars, 

 and the application of hands that set it a-going. The impetus of the hand, 

 applied at one end of the oar, and the resistance the water makes against the 

 other end, are both impressed on the point where the oar rests on the vessel. 

 This point is like the fulcrum of the common lever, which always bears the 

 sum of the weights at both ends, besides the weight of the lever itself; so that 

 the greater the effort is at one of the oars, and the resistance at the other, so 

 much the greater is the impression, which the point or fulcrum receives, in 

 order to its being put in motion. A galley, with two oars only, would go as 

 fast as it does with the usual number, provided the same number of hands were 

 applied with equal vigour to the two oars, and the oars were strong and broad 

 enough to make the necessary resistance; because then the fulcrum of the two 

 oars would receive as much impression as all the fulcra of the common oars 

 taken together. 



This consideration put me at first on contriving a way, how to apply a greater 

 number of hands to the common inclined oars; but, after several trials, I 

 threw them aside, and made use of perpendicular ones: because the first only 

 skim the water, and when the sea is rough, and the waves run high, they do 

 not take water often, and so become useless. For in this case the rowers are 

 tripped up, for want of meeting a resistance. 



This inconvenience is avoided by the revolving oars ; because they take the 

 water perpendicularly, and enter far enough not to miss it : and if the water 

 should happen to evade the stroke, the rowers would not be so incommoded; 



VOL. VI. 4 A 



