JOURNAL 



OF THE 



WASHINGTON ACADEMY OF SCIENCES 



Vol. io JANUARY 19, 1920 No. 2 



MATHEMATICS. — A trigonometric computer. F. E. Wright, 

 Geophysical Laboratory, Carnegie Institution of Washing- 

 ton. 



The solution of spherical triangles by the logarithmic compu- 

 tation of trigonometric formulas is at best a time-consuming 

 process, especially if there be many such triangles to solve. 

 In case high precision is required no other method is available; 

 but if only approximate results are desired, graphical methods 

 may be used, such as an exact projection net; of these the stereo- 

 graphic net published by G. W. Littlehales^ is the most accurate 

 and furnishes results correct to about 2' of arc under favorable 

 conditions. If the results are to be correct within one-half 

 minute of arc graphical methods are not adequate and recourse 

 must be had either to computation or to some mechanical device 

 of high precision. 



In crystallographic work the degree of precision is of the order 

 of magnitude of V^'- In the measurement of the changes in 



' Altitude, azimuth, and geographical position. J. B. Lippincott Company. 

 Philadelphia, 1906. 



29 



