LEVEL. 



placed into a framing of brass, which 

 operates as a spring to adjust it to the 

 level position, (/, by tlie action of the 

 large-headed brass screw, c. A stud 

 is affixed to the framing, and pushed 

 firmly into a gimlet-hole in the top of 

 the short rod, e, whicii is pushed or 

 driven into the ground at the spot 

 from whence the level is desired to 

 be ascertained. It need scarcely be 

 mentioned that the height of the eye- 



sight from the ground is to be deduct- 

 ed from the heigiit of observation. 



Fiir. 3 represents a useful and very 

 simple form of level. " A slip of 

 wood must be procured, measuring 

 three inches broad by half an inch 

 thick, and sixteen feet nine inches 

 long, which must be cut into foui 

 lengths of five feet three inches, five 

 feet, three feet three inches, and three 

 feet three inches, marked as follows : 



a a, five feet three inches ; b b, five 

 feet ; c d, three feet three inches ; e /, 

 three feet three inches : six thick 

 screw nails are also required, one 

 inch long. .loin c d and ef by a screw 

 nail, inserted about two inches from 

 the end of each, and exactly one inch 

 from their upper surfaces. From the 

 point i, upon c f, draw a line, meas- 

 uring thirty-six inches, towards/, and 

 exactly one inch distant from the up- 

 per surface, and divide this line into 

 thirty-six parts or inches. It is self- 

 evident that each of these points, 

 when elevated above c d, will show 



Q a 



a rise of one in fifteen, twenty, thir- 

 ty-four, &c., as the case may be, pro- 

 vided c d, which should be divided 

 into inches numbered on the upper 

 edge, shall be horizontal ; and e f 

 shall point to a pole or mark as high 

 above the ground as c d is; this is 

 efTected by fixing b h firmly upon c d, 

 at right angles, and either having a 

 plummet, g, suspended, as in the fig- 

 ure, or a spirit level fixed on the top 

 of c d. I prefer the plummet made 

 of bobbin or small cord, with a pierced 

 bullet at the bottom. The instru- 

 ment is retained in a level or hori- 



457 



