10 



10 



Pi*. 59 



Colored Figures 



In the larger illustration the met hod of reading the scale is more 

 pronouced. We observe the lower row of figures in reading toward 

 the left, and the upper row in reading toward the right. As in Figs. 

 N>, 57 or 58 and in all cases where double verniers are used, 

 there is offered to those who are less experienced, the constant in- 

 vitation to confusion and error in reading the wrong vernier. The 

 first precaution devised to overcome this hazard was to incline the 

 figures of both the limb and the corresponding vernier in the direct- 

 ion of observation. In 1910 we introduced the additional precaution 

 of coloring the R. to L. limb and its corresponding vernier figures 

 in carmine as indicated ah< 



Waterproof Construction 



Waterproof construction in every detail has been a 

 necessity for a great many years. The vernier w indows are set in 

 cement, the glass cover of the compass box is ' >.ahle and 



yet water tight", t the clearance between the horizontal plate is 

 reduced to less than 0.1 mm which excludes both dust and moisture 

 and the interior system of focusing has made it possible to protect 



t H'. /.. I'uHiinxs ; /"..' 0| 



Kll 



