78 Notices ref peeling New Booh, 



overfliot, half-overfhot, and underfhot wheels; by the dif* 

 ferent depths, curvature, and breadth of the troughs; the 

 different breadth of the float-boards in regard to the diameter 

 of the wheel; the height and thicknefs of the column of 

 water by which it is impelled; the greater or lefs velocity 

 with which the wheel revolves; its height as compared with 

 that from which the water falls upon it; the effect which 

 the water produces by its weight or its impulfe alone on the 

 wheel, &c. All thefe points mud be explained in a theo- 

 retical treatife to render it fufficiently ufeful, and before this 

 can be done it will be neceifary to make a great many re- 

 fearches, not merely founded on mathematical principles and 

 demonstrations, which may often millead the practical me- 

 chanician, but on incontettable experiments; and even if this* 

 fhould be fully accomplifhed, it would ftill be neceflary to 

 examine what ratio the refults arifing from experiments on a 

 (mall female bear to thofe made on a large fcalc. This ratio the 

 author has here endeavoured to determine with as much ac- 

 curacy as poflible. In regard to the fmall difference which 

 is fometimes obferved in experiments with fmall overfliot 

 wheels, on account of the attraction of the water by the float- 

 boards, and in confequence of which the action is fomevvhat 

 greater on a large fcale, the author, in order to obtain a cer- 

 tain formula, made various experiments on a large fcale, and 

 compared them with thofe of Polhem, Smeaton, and Boffut, 

 and his formulas with thofe of Karllen, Kaftner, Defaguliers^ 

 Belidor, Fabre, Elvius, &c. 



The whole work confills of three parts. — I. Mechanics. 

 The author here treats of the weight of bodies, and gives a 

 table of the weight of an ell of the different kinds of bar iron, 

 the weight of a cubic foot of water being 6i\ pounds: of 

 the different powers, and their action ; accelerated motion, 

 and the motion of falling bodies; the equilibrium of powers 

 that counteract each other: of compound motion; the refa- 

 ction and eoinpofitiori of pow crs ; the motion of bodies on 

 an inclined plane : of the motion of the pendulum ; the 

 centre of percuilion or point of ofcillation ; the circular mo- 

 tion of a body, and particularly the fly-wheel ; of the centre 

 of gravity, the lever, the pulley, the axle and wheel, the in- 

 clined plane, the wedge, friction, the flifTnefs of ropes; of 

 the power of bodies in a ftate of motion ; on the motion of 

 bodies which impinge directly againft each other; on the 

 impinging of hard and elaltic oodics ; of the motion of hard 

 and elaltic bodies, which impinge on each other obliquely; 

 and on eftimatino; the power of bodies which put machines 

 hi motion. — II. Hydrojlatics, This part treats on the preifure 



of 



