216 



MACHINERY IN CONNECTION WITH WATED. 



6 



J 



A leveling instrument for general use, siijficiently ac- 

 curate for all common purposes, may be made in the fol- 

 Fig. 239. lowing manner : Pro- 



'^ ' "ZIT "^' "^ T cure a mason's or car- 



6 penter's spirit-level, (a, 

 fig. 239) fasten it to the 

 upper side of a straight 

 bar of wood, and on the 

 ends of this bar secure 

 small, upright pieces of 

 tin plate, b, b, having 

 openings cut in the 

 centre. Horizontally 

 across these openings, 

 draw very fine wire, 

 which shall be exactly 

 at equal heights above 

 each end of the bar of wood, to adjust which, one should 

 be capable of sliding, and be screwed or wedged to its 

 place at pleasure. The bar is placed on a common com- 

 pass stafi*, as shown in 

 the cut, turning at the 

 ball and socket, below 

 the spirit level. A tripod 

 (fig. 240) is better, if it 

 can be had. A small 

 spirit-level should be se- 

 cured across the bar, so 

 that it may be adjusted 

 both ways. When the 

 bar is made perfectly 

 level, as shown by the air-bubble, by sighting through at 

 the two wires, the levelness or descent of the land may be 

 determined. 



To ascertain whether these threads are both of equal 

 heights above the bar, let a mark be made where they in- 



Fig. a40. 



