206 Ocean Magnetic Observations, 1905-16 



CRUISE II, JUNE 1910 TO DECEMBER 1913. 

 Magnetic Instruments. 



XII. For magnetic declination at sea. (1) Marine collimating-compass 1, same as for 

 Cruise I, supplemented by theodolite 5 from March 1911, for determination of constants on 

 shore ;^ (2) deflector 3, same as for Cruise I, supplemented by a special sighting device, in 

 use through March 1911, when it was replaced by deflector 4, but was kept on board subse- 

 quently for reserve and experunental use; (3) deflector 4, designed and constructed by the 

 Department of Terrestrial Magnetism, from April 1911, the same binnacle and tripod being 

 used as for deflector 3; (4) Kelvin dry compass-bowl, same as for Cruise I. The designa- 

 tions adopted, respectively, for the 4 compasses with appurtenances are CI, D3, D4, and 

 K. (5) Ritchie liquid compass 29971, provided with a brass binnacle-stand, by E. S. 

 Ritchie and Sons, was used as a steering compass for the vessel; (6) Ritchie liquid compass 

 29499, and (7) Ritchie hquid compass 29497, with azimuth circles same as for Cruise I, 

 were carried for reserve and experimental use; (8) Ritchie liquid compass 39670, provided 

 with brass binnacle-stand, by E. S. Ritchie and Sons, mounted in the chart-house from 

 September 1912. 



XIII. For magnetic inclination and total intensity at sea. (1) Sea dip-circle 189, same 

 as for Cruise I ;^ (2) sea dip-circle 203, same as for Cruise I,' until November 15, 1911, when 

 the dip circle with its needles was returned to Dover for overhauling; (3) sea dip-circle 204, 

 provided with dip needles 1, 2, 9, and 10, and intensity-needle pairs 7 and 8, and 11 and 12, 

 all by A. W. Dover, with improvements in design and construction specified by the Depart- 

 ment of Terrestrial Magnetism, was carried as a reserve instrument from October 1911; 

 (4) marine earth-inductor 3, provided with reversible gimbal-stand, all designed and con- 

 structed by the Department of Terrestrial Magnetism, from September 1912, supple- 

 mented by moving-coil marine galvanometer 19498 (tube 19499), by the Leeds and North- 

 rup Company, which was replaced in February 1913 by moving-coil marine galvanometer 

 20696 (tube 20697), by the Leeds and Northrup Company, metronome 309,^ telescope and 

 scale, and accessories. The designations adopted, respectively, for the four instruments 

 with their appurtenances are 189.9,10,75, 203.1234, 204.127S, and EI3. For the dip cu-cles 

 the intensity-needle numbers are italicized; for cases where both deflection and loaded-dip 

 observations were made the designation for the intensity needles is followed by a dagger 

 (t), thus, 189.9,10,7St. 



XIV. For horizontal intensity at sea. (1) Sea deflector 3, same as for Cruise I; (2) sea 

 deflector 4, provided with special brass binnacle-stand for use on board ship and tripod for 

 use on shore, all designed and constructed by the Department of Terrestrial Magnetism, 

 from April 1911, with deflecting magnets 45 and 2L of deflector 3, and new magnet 3 from 

 December 1912, and supplemented from September 1912 by Ritchie liquid compass 39670. 

 The designations adopted, respectively, for the deflectors are D3 and D4. 



XV. For magnetic declination and horizontal intensity on land. (1) Theodolite magnet- 

 ometer 2, same as for Cruise I; (2) theodolite magnetometer 4, same as for Cruise I; 

 (3) universal magnetometer 14, provided with all appurtenances and tripod 14, designed 

 and constructed by the Department of Terrestrial Magnetism, from April to September 

 1913; (4) universal magnetometer 19, provided with tripod 19, designed and constructed 

 by the Department of Terrestrial Magnetism, from September 1912 to May 1913; (5) 

 theodolite magnetometer 8, provided with tripod 8, by the Bausch and Lomb Optical 



'Between CruiBes I and II tripod 2 was modified bj- the addition of an arm rotating about the center spindle, on which 

 to mount the theodolite for the determination of constants on shore. ., , , 



2The brass gimbal-stand 2 was replaced in September 1912 by the special reversible gimbal-stand provided for marme 

 earth-inductor 3. 



^The axle of needle 7 was broken on May 14, 1911; needle 1 was returned to the Office m January 1911. 



^The metronome, originally intended as a timing device for maintaining constant speed of the rotation apparatus, was 

 fuuud unsuitable for use on board ship, and was replaced by a half-second chronometer. 



