FAST AND SLOW PLOWING. 131 



pears to apply to force required for cutting the earth, 

 And as the friction of the plow and the force exerted :n 

 cutting the earth have been found to be the greater 

 part of the whole draught, repeated experiments by the 

 dynamometer have proved that but little increased resist- 

 ance, as an average, occurs when a plow is drawn with in- 

 creased velocity ; the only additional power being that of 

 doing more work in a given time. For example, if a force 

 of 400 lbs. be required to draw a plow, whether at two or 

 at four miles an hour, then twice as much power only is 

 needed to plow an hour at four miles, as at two miles per 

 hour. In other words, no more actual force in amount is 

 necessary in most instances for a team to plow an acre in 

 four hours at the faster speed than in eight hours at the 

 slower. Hence the importance on the score of economy 

 in time, of employing horses that have a naturally rapid 

 gait, provided they possess full strength to overcome the 

 required draught with ease. Fast plowing, however, is 

 better adapted to stubble land than sod. 



THE DOUBLE MICHIGAN PLOW. 



The Double Michigan, called also the sod' and subsoil 

 plow, possesses some important advantages. The forward 

 or skim plow pares off a sod a few inches in thickness, 

 and inverts it into the bottom of the previous furrow. 

 The second or main plow follows, and throws up the lower 

 soil, completely burying the inverted sod and giving a 

 loose, mellow surface to the field. This forms an excellent 

 preparation for all crops, particularly carrots and other 

 roots, which grow best in a deep, loose bed of earth ; and 

 where a portion of the subsoil improves the top-soil by be- 

 ing mixed with it, a permanent advantage results. A 

 greater depth may be attained by the use of this double 

 plow than with one having a single mould-board, in sod 

 ground, because the inversion will be complete even if the 



