Geographical Maps and Sailing Charts. 



353 



which would be in every way satisfactory, as far as the prac- 

 tical use of the map is concerned, but it is believed that, in 

 case extreme accuracy is required, one would be well rewarded 

 by using the stereographic projection, especially as the labor 

 involved in making the map is a matter of no special con- 

 sideration. It took the writer less than three hours to make 

 all calculations necessary for laying out the map shown in 

 figure 23, and the work was done in duplicate in order to 

 check possible errors. The size of the original map is 16f by 

 12 inches, and, considered as projected on a central plane, 



23 



Outline Map of New York State in Stereographic Projection. 



figure 16, it is based upon a sphere of 15 meters, 49 feet, 

 diameter. The scale of miles adopted was based upon a dis- 

 tance of 3°, stereographically projected, measured from the 

 center of the map : this gave as one mile, 0*947 mm , or 0*037 

 inch. As a practical test of the accuracy with which measure- 

 ments may be made on such a map, six measurements were 

 made from the intersections of meridians and parallels, as 

 indicated on the map, and given in the table, as follows : 



