S. L. Penfield — Stereograjphic Projection. 



139 



numbers), each divided into tenths, with the exception of 

 the smallest space. It may be necessary to have spaces 

 of millimeters and a half similarly subdivided, which must 

 be determined by experience. For use, the scale of deci- 

 mal parts will be printed on a card. It is to be used in 

 locating points on charts corresponding to plates II and III, 

 where the meridians and parallels are given for every tenth 

 degree only. For example, to locate Queenstown, 8° 15' W., 

 51° 50' N., on plate IT, its longitude is determined by the diam- 



33 



eter 8° 15' W., and a short line on this diameter, drawn between 

 the parallels 50° and 60° N., locates the place in part. Making 

 use of the scale of decimal parts, figure 32, one of the spaces 

 (the 7 mm one) will approximate closely to the linear distance 

 between the 50th and 60th parallels, and the location of 

 Queenstown, nearly 2° north of 50°, can be determined with 

 considerable accuracy. Similarly, on a meridian projection, 

 plate III, the approximate location of any desired point between 

 the ten-degree spaces of the meridians and parallels can be 

 quickly ascertained. 



Finally, in fixing locations exactly by means of a needle 

 point, with reference either to the scale on the base line of 

 protractor ISTo. I, or to the scale of decimal parts, figure 32, it 

 is convenient to use a lens of low magnifying power, for exam- 

 ple, one of two-inch focus. A reading glass or pocket lens 

 may be employed, but, still better, a lens cut in two and 

 mounted on a stand, so that when placed upon the drawing or 

 chart it will be at the proper distance above the paper and does 

 not need to be held. By using only half a lens, the needle-point 



