172 Ocean Magnetic Observations, 1905-16 



CRUISE IV, MARCH 1915 TO SEPTEMBER 1916. 



After the completion of Cruise III, the Carnegie was out of commission for a few months, 

 during which time an observatory was built, just abaft the after dome, for the housing of 

 the new instruments used in the measurements of the electrical state of the atmosphere. 

 An additional stateroom on the starboard side of the cabin was provided for the accommo- 

 dation of an extra observer. The bottom of the vessel was sheathed with a copper alloy, 

 for tropical waters, and a belt, consisting of brass plates, was added to afford some protec- 

 tion against the ice conditions likely to be encountered on the forthcoming cruise. The 

 alterations were made at Hoboken by Tietjen and Lang, according to plans and specifica- 

 tions of the naval architect, H. J. Gielow, of New York, under the immediate super- 

 vision of J. P. Ault, as representative of the Department of Terrestrial Magnetism. These 

 improvements were satisfactorily completed by February 17, 1915, on which day the 

 Carnegie returned to her berth in Beard's Yacht Basin, at Brookljoi, to be put in commis- 

 sion. While the above work (PI. 17, Fig. 1) was being done the magnetic instruments 

 were examined, repaired, or altered in the Department shop as required for Cruise IV, and 

 their constants were redetermined. 



After a final inspection of the vessel by the Dii'ector and W. J. Peters, the Carnegie, on 

 March 6, left Brooklyn, under J. P. Ault's command, for Gardiners Bay, where she was 

 successfully swung on March 7 and 8, preparatory to putting to sea. This was the Car- 

 negie's fifth visit to Gardiners Bay for the purpose of swinging ship. The result of these 

 swings, made in 1909, 1910, 1913, 1914, and 1915, confirm the existence of local magnetic 

 disturbance in Gardiners Bay and furnish the desired control on the accuracy of the 

 magnetic work aboard the Carnegie. W. F. G. Swann remained on board to the last moment 

 to complete the installations and tests of the new atmospheric-electric instruments which 

 had been constructed in the Department shop for this cruise, in accordance with his 

 suggestions. In this work he was assisted by S. J. Mauchly and H. F. Johnston. 



The Carnegie sailed from Gardiners Bay on March 9, bound for Colon, Panama, the 

 ship's personnel being as follows: J. P. Ault, magnetician and in coimnand of the vessel; 

 H. M. W. Edmonds, magnetician and surgeon, and second in command; H. F. Johnston, 

 I. A. Luke, and H. E. Sawyer (who joined the vessel at Colon), observers; N. Meisenhelter, 

 meteorological observer and clerk; R. P. Doran, first watch officer; M. G. R. Savary, 

 engineer; second and third watch officers, 1 mechanic, 8 seamen, 2 cooks, and 2 cabin boys; 

 23 persons in all. In addition, S. J. Mauchly remained with the vessel until Panama was 

 reached, to perfect the installation and operation of the newly constructed atmospheric- 

 electric instruments. (On arrival of the Carnegie at Lyttelton in November 1915, Observer 

 Loring took the place of H. E. Sawyer, who was assigned to land magnetic work in Africa. 

 When the vessel, furthermore, returned to Lyttelton from the sub-Antarctic cruise. 

 Observer B. Jones joined the vessel in April 1916 in place of H. F. Johnston, assigned to 

 land magnetic work. A. Beech succeeded R. P. Doran as first watch officer in April 1916.) 



The passage to Colon was made in about 16 days, during which observations of at least 

 one magnetic element, and usually of all three, were made on every day of the stormy passage. 

 Two deaths from sickness occurred during this passage, namely, A. H. Sorensen, cook, 

 March 11, and W. Stevens, cabin boy, March 24. At Colon the ship instruments were 

 compared with the land instruments, and a new repeat station was estabUshed. Unfortu- 

 nately the previously occupied stations in the vicinity of Colon are now magnetically 

 affected by the large construction operations. On April 4 the Carnegie dragged both 

 anchors in a fierce norther, but finally the anchors held. She was subsequently towed to 

 a pier by the tug Porto Bella and the dredge Caribbean. (For view of shore work, see PI. 19, 

 Fig. 4.) 



The Carnegie was next taken through the canal and then she set sail in the Pacific 

 Ocean on April 12 from Balboa, bound for Honolulu. After 39 days at sea, during which 

 73 determinations were made of the magnetic declination and 39 each of dip and intensity, 



