Introduction 5 



Table 1 gives a summary of the land-survey work of the Department of Ter- 

 restrial Magnetism for the period 1905-1920. 



Table 1. Summary of Land Operations, 1905 to 1920. 



* Including expeditions engaged in minor operations and special work. 



The general methods followed, both for the observational and the computa- 

 tional work, have continued the same as described in Volumes I and II. The 

 instrumental equipments also, in general, have been the same as explained in the 

 previous volumes. Except for slight modifications, as noted, the results have 

 been tabulated in accordance with the conventions already adopted. The inter- 

 ested reader may be referred to Volumes I and II for any desired additional infor- 

 mation, also for specimens of observations and of computations and descriptions 

 of instruments. 



