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EQUIPMENT AND INSTRUMENTS 



4854 



Tlie map measure has several advantages over the m.ore common opisometer. 

 Its measuring wheel is only % inch in diameter so that very irregular lines may be easily 

 followed; it has a very free movement, so that it never slips; its movement is endless, 

 so there is no risk of its striking a stop suddenly; and it contains a scale. 



Distances on maps or sheets may be measured with the map measure as with the 

 older type of opisometer except that the centimeters or inches measured on the paper 

 may be read directly from the graduated scale and converted into statute or nautical 

 miles by the use of a factor. If the scale has been calibrated correctly — and this should 

 be verified before use — the registered distance in centimeters may be converted for 

 various scales by multiplying by the factors in table 11. 



Table 11. Map measure conversion table 

 [Multiply distances on map in centimeters by the factors for various scales to obtain statute or nautical miles.] 



4834. Lettering Sets 



Two types of mechanical lettering sets, manufactured under the trade names of 

 Wrico and Leroy, are furnished to hydrographic parties. Each type has its particular 

 advantages. 



With the Wrico set, letters and numerals, both vertical and slanting, are drawn 

 with a special pen through perforations in celluloid templates. A separate template is 

 furnished for each style and size of lettering. Some letters can 

 be drawn from a single setting of a template, but others 

 require two settings for completion. A spacing device on 

 one end of the template assures the correct placement of the 

 individual strokes of a letter as well as the correct spacing 

 between letters. The pen has a stylus point with ink reser- 

 voir, and is provided with a plunger to unclog the point. 

 While the pen is in use the plunger is raised free of the orifice. 

 Various-sized pens are furnished for letters of different 

 thickness. 



The Leroy set consists of templates with deeply grooved letters and numerals, and 

 a special adjustable three-legged scriber. One leg of the scriber follows the grooved 

 letters, a second leg follows a horizontal groove on the template, thus keeping the 

 lettering alined, and the third leg supports a stylus, with which the letters are drawn, 

 and a plunger. As with the Wrico set, pens of various sizes are furnished. A pencil 

 point attachment is also furnished for the scribing arm. 



Special symbols may be cut in both types of templates. For example, to adapt 

 the Wrico template for inking triangulation station symbols, a simple equilateral 

 triangle is cut in it; in the Leroy template the guiding triangle is cut through the first 

 lamination but in the shape illustrated in figure 96. A buoy symbol can be made 

 in a similar manner. 



Figure 96.— Triangulation station 

 symbol for Leroy template. 



