History of the Plow. 



115 



a cycloiJal arc is that which offers the least resistance to a 

 descending body, and it is hence deducible that an ascending 

 l)ody will pass up a cycloidal curve with less resistance than up 

 any other." 



This may be true, but wo have never seen any such demonstra- 

 tion. It is undoubtedly true that a body will fall through a 

 cycloidal arc in less time than any other. 



" The construction of our mould-boards is dependent on this 

 principle. In forming them we employ the cycloidal curve iu 

 two Avays, namely, to the formation of the concave of the mould- 

 board in the lines of ascent of the sward or furrow slice in the 

 act of plowing. The second application of the cycloidal curve is 

 in the convex curve along the sole of the plow, constituting the 

 part which enters and cuts the ground horizontally. In the 

 accompanying drawing. Fig. 70 represents a mould-board, A being- 

 its point and B its heel; 

 H the line A B is that of 

 the sole constituting the 

 lower edge which cuts 

 the furrow slice horizon- 

 tally. This curve in a 

 pjow which has been 

 essayed, and has been 

 found to answer well, was generated by a circle of eighteen 

 inches in 'diameter. 



" In Fig. 71 the curve C D E may represent the cycloid genera- 

 ted by the cii'cle F. The point 

 D, which is that of least curva- 

 ture, corresponds ^vitli the point 

 A of the plow Fig. 70, the 

 cycloidal line continuing to the 

 hind part or heel at B. It will, 

 no doubt, be advantageous to 

 vary the curve according to the nature of the soil — a point to bo 

 determined by experience — but whatever variation may be found 

 useful in this respect is still to be made in conformity with the 

 principle upon which we proceed, namely, that of making it 

 cycloidal. The line I H along the upper part of the mould-board 

 and in a plane parallel to that of the plane of the line A B, we 

 also make to fit the same cycloidal gauge. 



" In the plow that has been put in operation with a view of testing 



Ji'ig. 70. 



F'ig 



