34 TRANSACTIONS OP THE 



The map in question was constructed upon Mercator's 

 projection, but instead of the parallels and meridians being 

 straight lines at right angles to one another, they were arbi- 

 trarily-drawn curves. It was of course necessary to have a 

 key to this chart, which, upon being furnished, proved to be 

 very elaborate. Besides giving proper diagrams of the arbi- 

 trary lines, it gives the constants to be applied to individual 

 localities and their corrected latitudes and longitudes. On 

 the chart itself was a cryptographic statement of the neces- 

 saiy formulas for constructing the curves geometrically, re- 

 ferred to the N. E.-S. W. and N. W.-S. E. points of the com- 

 pass as axes. 



i 



