No. 4.] EVOLUTION OF FARM MACHINES. 251 



erly adjusted and there is loss of power. The sulky plow 

 has this advantage ; the wheels support the plow, causing 

 less pressure on the bottom of the furrow, uniform depth 

 and width of furrow, and the plowman can ride. The most 

 advanced form now in use in Massachusetts is the double 

 sulky, of which the National and Syracuse are types. The 

 most popular plow in the west is the tricycle, a plow sup- 

 ported by three wheels, of which the Flying Dutchman and 

 Canton Clipper are types. 



Points of a Good Plow. 

 Every plow is constructed to take a furrow of definite 

 dimensions, and can do good work only within narrow^ limits. 

 To select a plow wisely, the kind of work desired must be had 

 in mind. Some modern plows are made too narrow between 

 the land side and back part of the mold-board, and in sod 

 the first furrow taken out is too narrow to admit of receiving 

 the second furrow slice. If the furrow slice is of one- 

 third greater width than depth, it will be placed at an angle 

 of 45°. This arrangement exposes the largest possible sur- 

 face to the action of sun and air, and is considered most 

 advantageous for future cultivation. 



Harrows. 



The earliest form of the harrow used in this country was 

 undoubtedly the spike tooth fastened in an A-shaped or 

 square wooden frame. This form of harrow appears in the 

 modern smoothing harrows with teeth set at an angle to the 

 frame and turned back, or teeth that may be adjusted to any 

 desired position. The first step in advance was what was 

 known as the shares harrow, — share-shaped teeth, bolted to 

 an A-shaped frame, or a straight plank to be drawn at an 

 angle. This style of harrow may still be found in use, and 

 is being manufactured. A modified and improved form 

 appears in the Acme. 



A crude form of disc harrow has been used by the Japanese 

 from very early times. The disc harrow, now so commonly 

 used in this countrj^ has been evolved from harrows patented 

 by H. M. Johnson and S. G. Randall, from 1854 to 1859. 



