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Reports on Special Researches 



plates serve to exliibit, in a general way, how the cruises of the Galilee and the Carnegie 

 have been carried out, not only with reference to the other chief expeditions, but also in the 

 fulfilhnent of the object of securing, witliin a comparatively brief period, a systematic 

 magnetic survey of ocean areas. On the homeward cruise of the Carnegie in 1916-1917 

 (see broken red lines, Pis. 23 and 24), additional data will be obtained. 



Figure 29 shows the corrections of the various magnetic-declination charts for certain 

 portions of the Atlantic Ocean at the time Cruise I and the first part of II of the Carnegie were 

 carried out. East magnetic dechnation being given the positive sign, a plus correction, for 

 example, means that the chart-value of east magnetic dechnation was smaller and of west 



Cmse n, 1910-11 



Rio de Janeiro 



Buenos Aires 



CapeToiun 



gOocT" ' 12000 - Nautical milej 15OQO 18000 



Fig. 29.— Showing Corrections of Magnetic-Declination Charts for the Atlantic Ocean, 1909-1911. 

 (British Admiralty, -; United States Hydrographic Office, ; German Admiral t.v, •) 



magnetic dechnation larger than the values observed on the Carnegie. The Carnegie's 

 chief ports of call are shown, as also the distances in nautical miles traversed from the 

 home port. New York. The chart-values used in the construction of Figure 29, as well as 

 of Figures 30-35, were referred to the dates of the Carnegie's observations by means of the 

 secular changes shown on the respective charts. 



It will be seen that the curves given in Figures 29-35 are usually the same for the 

 various charts, the corrections being generally less than 2°, though in some instances they 

 are more. The pecuhar and often systematic run of the corrections for long stretches is 

 well shown by the curves. Figure 30 applies to the regions of the Atlantic Ocean traversed 



