SURVEYING INSTRUMENTS. 



89 



tions from the ends of the brass tube in which it is enclosed, 

 and thus affording facilities for accurate adjustment. 



They are made sometimes with sights at each end, and 

 adapted to a staff, serving for conducting small parcels of 

 water, draining a field, &c. 



The adjustment of these levels is very easily proved, or 

 made, by bringing the bubble in the middle, upon 

 any table, or base ; if upon reversion in the same 

 place precisely, the bubble keeps to the middle, 

 it is adjusted ; if not, turn one of the screws at 

 the end, till it be so raised or depressed as to 

 cause the bubble to stand the reversing, at the 

 same time altering the inclination of the plane on 



which the level is tried. 



Price, $2 to $6. 



The Masons' or Carpenters' Level. (Fig. 102.) 

 This spirit level is mounted in a mahogany 

 stock, or frame, usually from Fig. 101. Fig. 102. 

 one to two feet long, but some- 

 times as small as three inches ; 

 the glass tube is sunk in the 

 wood, and cemented fast ; a 

 stout brass plate covering the 

 wood around, leaving a long 

 aperture through which to view 

 the bubble ; occasionally the 

 ends of the wood are capped 

 with stout brass, to prevent 

 wear. 



They are made sometimes 

 with sights, for the purpose of 

 sighting through for levelling 

 long distances. 



Price, 88cts. to $1.50. 



The Level and Plumb. (Fig. 

 103.) This is made similar to 

 the last, with the addition of a 

 cross level, for which the stock 

 is made a little wider ; the cross 

 level is enclosed in a tube and 

 accurately fixed in the stock, 

 having a large circular or semi- 



