3i6 DESCRIPTION OF A MOULD-BOARD. 



Let the breadth and depth of the furrow the farmer 

 ufually opens, as alfo the length of his plough-bar, from 

 where it joins the wing to the hinder end, be given ; as 

 thefe fix the dimenfions of the block of which the mould- 

 board is to be made. Suppofe the furrow 9 inches wide, 

 6 inches deep, and the plough-bar 2 feet long. Then 

 the block, Fig. i. muft be 9 inches |wide at bottom [b. c.) 

 I3|- inches wide at top, {^a. d.) becaufe if it were merely 

 of the fame width with the bottom as a. e. the fod, only 

 raifed to the perpendicular, would fall back into the fur- 

 row by its own elallicity. I find from experience, that, 

 in my foil, the top of the mould-board fliould overjet the 

 perpendicular 4-i- inches in a height of 12 inches, to 

 infure that the weight of the fod fhall preponderate over 

 its elaflicity. This is an angle of nearly 22°. The block 

 mufl: be 12 inches high, becaufe, unlefs the mould-board 

 be in height double the depth of the furrow, in plough- 

 ing friable earth, it will be thrown in waves over the mould- 

 board : and it mufl: be 3 feet long, one foot of which is 

 added to form a tail-piece, by which it may be made faft 

 to the plough-handle. The firft operation is to give the 

 firfl: form to this tail- piece, by fawing the block. Fig. 2. 

 acrofs from a. b. on its left fide, (which is 1 2 inches 

 from its hinder end) along the line b. c. to c. within 14. 

 inches of the right fide, and to the correfponding point in 

 the bottom, \\ inches alfo from the fide. Then faw in 

 again at the hinder end from d. e. (i-i inches from the 

 right fide) along the line d. c. The block a. b. c. d. e.f. 

 g. drops out and leaves the tail-piece c. d. e. h. /. k. \^ 

 inches thick. The fore part of the block <?. b. c. k. I. m. n. 

 is what is to form the real mould-board. With a car- 

 penter's fquare make a fcribe all round the block at every 

 inch. There will of courfe be 23 of them. Then from 

 the point k. Fig. 2. and 3. draw the diagonals k. m. on the 

 top, and k, 0. Fig. 3. on the right fide. Enter a faw at 



the 



