DKVICKS, APPI^IANCES AND CONTRIVANCES. 409 



the wings need not be more than one-half as wide as 

 drawn, and should also extend under the bottom. For 

 variations make B with only three outside boards, or 

 make the outside jacket to extend only about one foot 

 on the first box, just sufficient 

 to hold the gate in position. 



Simple Grade Levels. 

 — A cheap and accurate lev- 

 eling instrument and a tar- 

 get or sighting- rod, like that 

 shown in Fig. 100, can be 

 made by any one with a little 

 ingenuity. This is simply 

 a sharp shaft or stake, B, 

 with cross-bar. A, bolted 

 firmly to it. C is a rubber 

 tube attached to the staff and 

 passing up through a hole at 

 each end of the cross-bar. 

 At each upper end of this 

 rubber tube is a glass tube, 

 say four inches long, with 

 the rubber tubing stretched 

 or sprung around it so as 

 not to leak. Colored water fills the tube, and in 

 leveling it is only necessary to sight across the tops of 

 the colored water to the target and take levels just as 

 with a $25 surveyor's level. 



For short distances it is accurate enough. The 

 glass tubes may be corked tight about an inch above 

 the colored water to prevent its escape when the level 

 is carried. Of course a carpenter's spirit-level, instead 



FIG. 99 — THE VAN HORN 

 TAP GATE. 



