THE CONQUEST OF TIME AND SPACE 



Early in the twentieth century an American ship, 

 christened the Carnegie^ in honor of the philanthropist 

 who supplied funds for the enterprise, was constructed 

 for the express purpose of making accurate charts of 

 the lines of magnetic declination in various parts of the 

 globe. This ship differs from every other vessel of 

 considerable size ever hitherto constructed in that no 

 magnetic material of any kind was used in connection 

 with its structure or equipment. For the most part 

 iron was substituted by copper or other non-magnetic 

 metal. Pins of locust-wood largely took the place of 

 nails; and wherever it was not feasible to do away with 

 iron altogether it was used in the form of non-magnetic 

 manganese steel. The purpose of the Carnegie is to 

 provide accurate charts of magnetic declination for the 

 use of navigators in general. The value of observa- 

 tions made with this non-magnetic ship will be clear 

 when it is reflected that with an ordinary ship the 

 observer can never be absolutely certain as to what pre- 

 cise share of the observed fluctuation of the compass is 

 due at any given moment to the ship's influence. In 

 other words — using technical terminology — he can 

 never apportion with absolute accuracy the influence of 

 declination and of deviation. Yet it is highly important 

 that he should be able to do so, inasmuch as the decUna- 

 tion of the compass is an all-important element in reckon- 

 ing the exact location of the ship, and would be the same 

 for every ship at that place, whereas deviation denotes 

 a purely local disturbance which would never be the 

 same for any two ships of different construction. 



Not only does the magnetized needle thus tend to 



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