4 Ocean Magnetic Observations, 1905-16 



Passing over various subsequent expeditions, we come to the most serious 

 and first really important undertakings for magnetic science in general, viz, those 

 of the Erebus, the Terror, and the Pagoda, from 1840-45, chiefly in the southern 

 oceans. Here we have the first elaborate attempt at determinations of the three 

 magnetic elements at sea, the Fox dip-circle for measuring the magnetic incUnation 

 and intensity at sea having just been devised. This most carefully executed work 

 was done under the direction of Sabine, the famous EngUsh magnetician, who did 

 so much for the advancement of magnetic science. Not only was the work ably 

 directed, but the commanding officers of the vessels, one of whom was Captain 

 Ross, the discoverer of the North Magnetic Pole, were most zealous and painstaking. 

 The attempt was made to obtain full series of observations daily, and these were 

 secured at times under great physical difficulties, as, for instance, in the Antarctic 

 regions. The ships were repeatedly "swung," and every attempt was made to 

 determine accurately the de^dation constants. 



It will be of interest to point out in this connection that it was not alone the 

 devising of an instrument for measuring the magnetic incUnation and intensity at sea 

 that made this memorable and remarkable work possible, but also the elaboration of 

 the mathematical theory of the deviations arising from the unavoidable iron on 

 board a vessel, pubhshed byPoisson a year before the inception of the survey in 1839. 

 Working with Poisson's formulae, Archibald Smith, at Sabine's request, put the 

 determination of the various necessary corrections in a practical form, so that they 

 could be successfully applied. 



The expedition of the Austrian frigate Novara secured a valuable series of 

 decUnation data while ckcumnavigating the globe in 1857-60. 



Next were the two notable expeditions of the Challenger in 1872-76 and the 

 Gazelle, a German vessel, in 1874-76. Both of these made observations of the three 

 magnetic elements over various ocean regions. 



Reference should also be made to the important work done by the naval serv- 

 ices of various countries, which can not be described here in detail, and to the obser- 

 vations of later Antarctic expeditions, notably those of the Discovery and the Gauss. 

 The work of various vessels of the Coast and Geodetic Survey also deserves 

 notice, for it was the successful inauguration of the magnetic work on these ves- 

 sels, in 1903, which gave me the requisite experience for undertaking the ocean 

 magnetic survey of the Carnegie Institution of Washington. Since 1903, these 

 vessels have utiUzed every opportunity in passing from port to port, while engaged 

 on their regular surveying duties, to determine the three magnetic elements. Thus 

 valuable series of observations have been obtained along the Atlantic and Pacific 



coasts and in the Gulf of Mexico. 



L. A. Bauer. 



