History of the Plow. 87 



of the mould-lioard join, which is shown in the figure by the line 

 h d, touches the surfiice the whole distance in an even and 

 uniform application, and leaves no sinking or protuberance in any 

 part of the distance, so, at a distance half way between the 

 diagonal line just described and th3 angle between the first and 

 second sides, a line, f g, drawn parallel to the diagonal line 

 already mentioned will receive the chalked string as on a uniform 

 and even surface. In like manner, if a point be taken one inch 

 behind the angle connecting the second and third sides, and a 

 perpendicular, h t, be raised upon it, that perpendicular will 

 coincide with the vertical portion of the mould-board in that 

 place ; or, in other words, if a plumb-line be let fall so as to 

 reach a point one inch behind the last mentioned angle, then such 

 plumb-line will hang parallel with the mould-board the whole 

 way; the line of the mould-board there neither projecting nor 

 receding, but being both a right line and a perpendicular line. 



Moreover, if a right line be drawn from a point on the just 

 described perpendicular, one inch or thereabouts above the upper 

 margin of the fourth side, and from the point to which the said 

 perpendicular, if continued, would reach, if the said J. Wood 

 repeats a right line, k I, be drawn downwards and forwards, not 

 exactly parallel to the diagonal herein already described, but so 

 diverging from the same that it is one inch more distant or 

 farther apart at its termination on the fifth side of the mould- 

 board than at its origin or place of beginning, such line so 

 beginning, continued and ended is a right line parallel to the 

 mould-board along its Avhole course and direction, and the space 

 over which it passes has no inequality thereabout. 



If the mould-board be measured and proved vertically and 

 obliquely by the saw in fashioning it, and by the rule in meeting 

 it, and by the chalk line in determining it, the capital and dis- 

 tino-uishino- character of rio;ht lines extendino; on, over and alono; 

 the peculiar curve which his mould-board describes is always and 

 inseparably present. 



/Second Specijication. — A cast iron standard for connecting the 

 mould-board with the beam: It rises from the fore and upper 

 part of the mould-board, being cast with it, and being a projection 

 or continuation of the same from where the fourth and fifth sides 

 meet. By a screw-bolt and nut properly adjusted above the top 

 of the standard, and acting along its side, assisted, if need require, 

 l^v a wodo-o for tiirhtcnino- or loosonino-, the beam may be raised 



