DEPARTMENT OF TERRESTRIAL MAGNETISM. 303 



To facilitate the time work and control of timepieces by Mr. J. J. 

 Capello, property and shipping clerk, a wireless outfit to receive signals 

 from the ArHngton station was designed and constructed by Mr. 

 Sterling and installed in the chronometer room. 



Besides the special reports for Volume IV, mentioned on page 

 299, in which members of the division took part, the following 

 additional reports were prepared: Results of examination of sites for 

 magnetic observatories, compiled by J. A. Fleming; construction of 

 non-magnetic experiment building, by J. A. Fleming; auxiliary tables 

 to facilitate revisions of field magnetic observations, by H. W. Fisk; 

 discussion of corrections on standard for dip-circle needles, by H. W. 

 risk; discussion of magnetometer corrections on standards in declina- 

 tion and horizontal intensity, by J. A. Fleming. Others not elsewhere 

 mentioned who have been assigned temporarily from time to time to 

 the division and who have contributed to the work done were Messrs. 

 D. M. Wise, J. L. Trisler, H. B. Hedrick, M. B. Smith, and A. J. S. 

 Dixon. 



INSTRUMENT WORK.^ 



The work in the instrument shop during the year may be roughly 

 classified as follows: equipment, 30 per cent; experimental, 20 per 

 cent; improvements and repairs of instruments and buildings, 43 per 

 cent; miscellaneous and stock, 7 per cent. 



The new construction included: sine galvanometer No. 1 for the 

 absolute determination of horizontal intensity and special appliances 

 required in determining the constants, non-magnetic heating arrange- 

 ments and current-distributing arrangements for the Experiment 

 Building, and an apparatus for producing harmonic motion in connec- 

 tion with the investigation of dynamic effects on instruments mounted 

 aboard ship. Especial attention had to be given to the details of pre- 

 cise working of marble for the coil mountings of the sine galvanometer 

 and to the providing of the strictly non-magnetic materials required 

 for its construction. 



The experimental work was concerned chiefly with the development 

 of special apparatus for the experimental work under Dr. Barnett's 

 direction and to the development of the marine earth-inductor and of 

 galvanometers suitable for use with it at sea. The first attempts to 

 make use of the string galvanometer on board with the earth-inductor 

 were not successful, because the only fiber available had too great 

 resistance. Pending the development of methods to produce sput- 

 tered quartz fibers of suitable resistance by Dr. Mauchly (see p. 309), 

 improvements were made in the design of the moving-coil type of 

 marine galvanometer previously used. Tube 19499 was reconstructed 

 and new coil with special fiber-clamping arrangements provided, so as to 



Trom the report of the chief of the Magnetic Survey Di-\dsion, under whose charge the instru- 

 ment shop is placed. 



