DEPARTMENT OE TERRESTRIAL MAGNETISM. 203 



circles, and i earth inductor. This work has been done invariably by the 

 method of simultaneous comparison with standard instruments. The instru- 

 ments used for the observations in atmospheric electricity on board the Car- 

 negie have been tested and standardized. The various forms for sea and 

 land work have been carefully revised and improved and new forms devel- 

 oped to facilitate as well as to give greater uniformity of method for all 

 observations and reports. General and particular instructions have been 

 prepared as necessary. 



The compilation of past magnetic data, the indexing of current literature, 

 and abstracting of publications of especial interest have been continued. 

 Requests for data and information have been numerous and varied ; responses 

 have been made as promptly and in such detail as has been possible. The 

 Government trigonometrical survey of Southern India has been supplied for 

 mapping purposes with the data obtained in Persia; a preliminary isogonic 

 chart of the North American continent has been constructed at the request 

 of Professor Chant, of the University of Toronto ; ocean magnetic data have 

 been supplied the hydrographic offices of various governments ; details of 

 instrument construction have been supplied to the United States Geological 

 Survey ; tests of improved forms of compass needles have been made for 

 manufacturers of surveying instruments, etc. 



Some time has been given to the magnetic work to be undertaken in co- 

 operation with Capt. R. Amundsen in his coming polar expedition and the 

 preparation of the magnetic outfit, the observer-in-charge. Dr. H. M. W. 

 Edmonds, being engaged at the office from January to June partly on this 

 special work and partly on the regular work of the Department. Extensive 

 preparations were made for the work to be taken up in South America and 

 in China in the present and coming years. In connection with the alterations 

 of the Carnegie, much attention has been given in the office to the perfection 

 of details, consideration of materials, tests, and plans. 



SHOP WORK. 



Magnetometers Nos. 12, 13, 14, and 15 have been completed during the year; 

 No. 15 was constructed at the request of the Canadian government for the 

 use of the meteorological service of Canada. These instruments have been 

 found very satisfactory and their portability and light weight makes them 

 peculiarly suited for survey work in countries where transportation is diffi- 

 cult. Magnetometer No. 14 is a universal instrument of new design; it is 

 suited for the determination of all the magnetic elements and geographical 

 position and azimuth. The weight of this instrument with its accessories, but 

 without packing, is under 15 pounds; the packing will increase this to about 

 30 pounds (the instrumental outfit and packing heretofore used in the earlier 

 work of the Department weighs considerably over 100 pounds ; thus some 

 idea of the compactness of the present outfit may be obtained). Magnet- 

 ometers Nos. 12, 13, and 15 were especially designed as theodolite magnet- 



