116 Report on Trials of Plows. 



the principle, the lines of the ascent of the furrow slice which 

 govern the concavity of the mould-board, were regulated by a 

 cycloidal gauge made to a curve generated by a circle of sixteen 

 inches in diameter. Let C D G, Fig. 71, represent such a gauge, 

 and the lines a^ a^, &c.. Fig. 70, be assumed as those of the ascent of 

 tlie furrow slice on the mould-board; in formino^ said board we 

 place the gauge in the direction a' with the part D, which is that of 

 least curvature at a', and thus proceed on until we arrive at the 

 hinder part, B H, withdrawing or lowering the gauge at its lower 

 end at each successive application, so that a small ^lortion of the 

 least curved portion towards D, and a larger portion of that 

 towards C shall touch the mould-board; these successive depres- 

 sions may be indicated by the divisions at D upon the gauge. 

 The degrree in which the mould-board shall curve and hang^ over 

 at H for turning the furrow slice may be varied according to the 

 judgment of the maker, the curvature being governed by the 

 diameter of the o-eneratino- circle and the deo:ree in which the 

 gauge is depressed at every successive application of it. 



" Having thus fully set forth the nature of our invention, and 

 shown the manner in which we carry the same into operation, 

 what we claim therein is the giving to our mould-board the seg- 

 ment of a cycloid convexly on its face in a line leading from front 

 to rear, and concavely in the lines of the ascent of the furrow 

 slice." 



Eemarks by the Inventors. 



"The main object is to pulverize the soil" — (they are the first 

 who have made this avowal among inventors) — " and the onl}' way 

 in which this can be eftected is by bending a furrow slice on a 

 curved surface" — (this is the first allusion that we have met with 

 to the influence of the shape of the surface in cracking the soil) — 

 "so formed that it shall also twist it somewhat in the manner of 

 the screw. Such a surface will be formed by taking a strip of 

 iron and twisting it after the manner of a screw auger; and if 

 there is given to this piece of iron a greater twist at one end than 

 the other, cycloidal curves may be thereby produced. Now as 

 the curvature of the cycloidal mould-board generally increases 

 from the lowest to the highest point of ascent, it follows, neces- 

 sarily, that the furrow slice, in passing along it, will ])e more and 

 more bent as it ascends. By forming the fore part of the mould- 

 board by means of that point of the cycloidal gauge which has 

 the least curvature and the hinder part b^- tiiat portion which lias 



