Mr. Mouchette is just returned. I sincerely congratulate you upon the success of the engine of which he gives the most favourable report & fully justifies yr. confidence in your engines. I am sufficiently sanguine to hope that all difficulties are now vanished. Knowing our power nothing remains but adapt the vessel to it. In attempting this hitherto we have deceived ourselves by wandering into the field of conjecture rather than adhereing to plain calculations & we shall still do so if we expect that the present engine will turn the wheels we now have 80 times in a minute, as will appear from this calculation. Our wells contain exactly 60 cubic feet of water. The whole of this is set in motion at every revolution of the wheels with a rapidity equal to the main motion of the arms, that is if the wheels make 80 revolutions in a minute at the rate of 8 miles an hour. Now as the boat will not remove more than 20 feet of water if she goes 8 miles an hour, if it was possible to move the wheels as they are now constructed 80 rounds in a minute we should throw away one half of our power, for the boat could not move faster than the water in the wheels & the power would be uselessly expended in throwing out water unnecessarily. But it will be found on experiment that however perfect our engine is, it cannot turn the present wheels 80 times in a minute. The wheels then must necessarily be altered or the motion rendered still slower. To make the motion slower is to diminish our chance of moving the boat fast because she will at no rate move faster than the water in the wheels though she may be made to move as fast as I have found on actual experiment. The wheels then must be altered, not by making the arms shorter for this would diminish their motion, besides that it would require an alteration in the boat—but by diminishing their depth. They are now if I recollect 18 Inches deep, let them be reduced to nine Inches. Let the motion of the wheels by no means exceed 80 nor be lower than 70 turns in a minute and I will answer for the success of the experiment, & upon the whole it will turn out a fortunate discovery since we shall find that our wells need not be above half the size we have made them & of course much room and much weight of water be saved in future. That we have erred hitherto should not discourage us. It is the fate of all new undertakings and it is happy when the error can be so easily discovered & detected. Another circumstance of considerable moment must be attended to. If the diminution of the motion is brought about by changing the sun and planet wheels, one half the motion of the flys will be lost & they rendered almost useless from this circumstance. If they are made heavier they will overload the boat.