152 MECHANICS. 



ing the seed, which is distributed through holes in the 

 zinc bottom by the vibrations of a notched rod, and 

 any desired quantity of seed accurately regulated. 



HORSE-RAKES. 



In all labor-saving contrivances, the greatest advant- 

 age is gained where the work originally performed by 

 the hand is light, or where much exertion of strength 

 is not required. An example of this kind occurs in the 

 use of hand-drills for sowing small seeds, such as tur- 

 nips and carrots. These, when planted by the unas- 

 sisted hand, require but little power, but the operation 

 is very slow. A hand-drill enables the laborer to apply 

 his whole strength profitably, with an increase in ef- 

 fect of at least forty or fifty times. A similar advant- 

 age is gained by the use of the horse-rake, where the 

 full strength of a horse is made to accomplish the 

 moderate labor of the hand-rake, and to perform an 

 amount equal to at least ten men. With the simplest 

 form of the horse-rake, sixteen acres of heavy hay have 

 been collected by one horse in a day, and with the re- 

 volving-rake, twenty to twenty-five acres. 



The simplest form of the horse-rake is represented in 

 Fig. 130. It is made of a piece of strong scantling 

 three inches square, tapering slightly toward the ends, 

 for the purpose of combining strength with lightness, 

 and in which are set horizontally about fifteen teeth, 

 twenty-two inches long, and an inch by an inch and 

 three fourths at the place of insertion, tapering on the 

 under side, with a shght upward turn at the points, to 

 prevent their running into the ground. The two outer 

 teeth should be cut off to about one third their first 



