On the Reduction of Horse Labour Iry siufjle Carts. 77 



lower the load, and tlie more lengthened its base, the less dis- 

 turbed will be the equilibrium ; and that, consequently, the less 

 will be the pressure. And again, that the higher the load in 

 proportion to its base the greater the pressure. To prove this, 

 take a plumb-line, and drop it to the point of the axle ; this will 

 divide the load into two unequal parts, the downward side being 

 the greater, and the upward the less : the difference between 

 them is the weight of pressure. To find the amount of it, draw a 

 second line from the axle at right angles with the inclined plane : 

 this will pass through the middle of the overbalance, will deter- 

 mine the position of the pressure, and will divide it into two 

 equal parts : and it will distinctly exhibit one of these half-parts 

 by the angle it forms with the plumb-line. And if on this 

 second line the centre point of weight of pressure be found (and I 

 think it resides in the centre of the area formed by the above 

 angle doubled) and from it an arc be described to the horizontal 

 lever, the shaft, or rather to a line resting on the horse's back at 

 one end, and on the middle of the wheel at the other, there will 

 be seen the exact share of weight that each of these two support- 

 ers bears. 



To elucidate this, the following figures are represented on the 

 same inclined plane, and supposed to be loaded with hay from 

 the field, in perfect equilibrium on level ground. The moment 

 that a pound weight inclines off the balance it passes the plumb- 

 line E, and becomes two pounds of pressure. And the equal 

 division of that pressure is exhibited by B> the line at right angles 

 with the inclination ; and its position and contents are determined 

 by the triangle E C D : e is the centre of the weight of pressure, 

 D A '\s the lever borne by the cart-saddle A, and the wheel D ; 

 and 0 the amount of pressure that descends upon it. 



I do not vouch for exactness, nor for a correct delineation of 

 the loaded carts, yet I have endeavoured to make the following 

 calculations as fairly as I could, upon a scale of one-eighth of an 

 inch to a foot. For simplicity I have left out the weight of the 

 cart bodies, though I have considered them as bulk where they 

 come within the angles of pressure. 



Fig. 1 is a midland county two-horse cart, containing a load of 

 green hay, 5 yards long x 2 high x 3 Avide — 30 cubic yards — 

 about 1 ton; and showing by the plumb-line E that on the slope 

 on which it is descending there exists in the triangle E CD about 

 747 lbs. of pressure, which falling from the centre of weight, e, 

 on the lever DA at o, gives the horse A the burden of -fi- of this 

 weight, and the wheel D f g ; therefore that the horse sustains on 

 his back 456 lbs. 



Fig. 2, a Cumberland single-horse cart, with its usual load of 

 the same material, 3^ yards long x If liigli X 2 J wide =15 



