16 



SKETCHES OF RURAL AFFAIRS. 



Another important part of the plough is the mould- 

 board. This rises very gradually from the fin in an 

 oblique position, either to the right or left : its use is 

 to push aside and turn over the slice of earth just cut, 

 so as to leave a regular furrow wherever the plough has 

 passed. Originally this part of the plough was, agree- 

 ably to its name, a mould-board, defended with plates 

 of iron, but it is now made wholly of cast iron. Small 

 was a great improver of this part of the plough, and 

 constructed it on true mechanical principles. He in- 

 vented a plan for discovering the true shape which 

 ought to be given to the mould-board by making it of 

 soft wood, and then carefully observing, during many 

 trials, the parts most liable to pressure or to friction ; 

 this gave him hints for the construction of his cast-iron 

 mould-board, which has a regular curve or twist, well 

 adapting it for turning over and placing the furrow- 

 slice exactly in the right position, while it also lessens 

 friction in the work. It was a happy circumstance that 

 just at that time the founding of cast iron was getting 

 very general ; Small took advantage of it, and framing 



MOULD- BO .VRD OR TURN-FURROW, 



icith the Share annexed. 



a mould-board, &c., of cast iron, he thus obtained 

 patterns according to which any number of similar 

 forms might be constructed. 



