Sec. 8.] HORSES AND HARNESS. 121 



between the tlirco liorses. The English have what are called compensating 

 bars between the swing-bar (which we call the double-tree), and the three 

 single-trees, so that each horse may be seen to pull equal to the others. 



These bars should be made of iron, one and a half inches wide and three 

 eighths of an inch thick. Two of the bars are each 27 inches long, and these 

 are attached, as the single-tree usually is, to the eiiils of the swing-bar, by a 

 fulcrum just one third of the length from the outer end. Then a center 

 bar, 20 inches long, is attached by working joints to the ends of these out- 

 side bars, and the single-tree of the center horse is attached to the center 

 of this bar, and the single-trees of the outside horses are attached to the 

 ends of the other bars. This crpializes the strain upon all the horses, for it 

 is impossible for one to start ahead without imparting motion backward to 

 both of the other horses. 



Tlie irons of a single or double-tree should always be made so as to clasp 

 the wood, which should never have a hole bored through it to pidl by. 



171. DimeiisiOKS of Double aiul Siaglc-Trces. — Perhaps every farmer knows 

 how to gear a horse, and what are the proper dimensions of a set of douljle 

 or single-trees. But there arc many persons who take to farming in after- 

 life, and others who may have occasion to make this part of a set of horse- 

 geai'ing, and these will be glad to have (he following directions to refer to. 



The bar of a double-tree should be three feet nine inches long and tliive 

 and a half inches wide at the center, and one and a quarter inches thick, and 

 it should be made of the strongest kind of wood that can be procured, and 

 straight grained and free from knots. The best M'ood we have for tliis ])ur- 

 pose is second gi'owth white ash, such as all of our best hoc and shovel 

 handles are made of in the United States. 



A singlc-trce should be three feet three inches long, two and a half inches 

 wide, and one and a quarter inches thick. The irons of double and single- 

 trees may be all jnade of the same form and strength ; that is, a piece of the 

 very best flat bar iron, one and three quarter inches wide and one fourth 

 of an inch thick, is bent so as to clasp around the back part, and the ends 

 come altout two thirds of the width toward the front edge, with lialf-inch 

 holes througii the end and through the wood. In this hole a jMcce of half- 

 inch iron is to be inserted by tapering the ends so that they will go through 

 the hole from each way and clinch fast on the flat iron, leaving the bend 

 i'orward so aa to form a loop in which to ])Ut the hook of the single-tree, or 

 the chain, or a loose ring, as may be required. These irons can not come 

 off, even if they should get loose, and the wood is not likely to break, be- 

 cause there is no strain upon it. Tiie strain is all upon the irons, and when 

 the loop wears out, U new one is easily inserted in its place. The center irons 

 of the double or single-trees arc ]nit on after tiic same fashion, tiie loo]) of tlie 

 round iron being back, instead of forward, and both the Hat and round irons 

 for the center nuiy be a little stronger than the ends. 



This plan is far better than m.aking the irons to drive on like a ring, fast- 

 ening them by a few stub-nails driven in the end of the singlc-trce. Acci- 



