THE VESSEL 21 



They communicated directly with the chart-room, so that, with 

 their protection, the observers could go about their work regard- 

 less of wind or rain or spray. On the Galilee, an ordinary sailing 

 vessel chartered for a magnetic survey of the Pacific between 

 1905 and 1908, instruments had been mounted on an open plat- 

 form above the deck. These domes were partly responsible for 

 the choice of the square-rigged foremast, for they would have 

 interfered with the handling of a boom forward. This choice 

 of sail was of course unfavorable when sailing close to the wind 

 for long passages, but with a light breeze blowing from astern she 

 was more than a match for a schooner. 



Besides these observatories, the super-structures included: 

 A chart-room housing the "standard" compass, navigating in- 

 struments and charts; three laboratories for the atmospheric- 

 electric, chemical, and radio investigations; and a "control-room" 

 on the quarter-deck housing the observation-control apparatus 

 of the sonic depth-finder together with certain parts of the mag- 

 netic and meteorological equipment. 



Below deck, from the bow toward the stern, were the forecastle, 

 the forward galley, the wardroom with officers' quarters, the 

 cabin with staterooms, the after galley, the fuel tanks, the engine- 

 room, and the lazarette in which provisions were stowed. 



Before we describe the scientific instruments, we might answer 

 the first question asked by the average visitor to the ship : Why 

 was the Carnegie built non-magnetic? Iron in a vessel's hull, or 

 carried on board, affects the compass-needle in two ways. First, 

 it alters the normal direction of the needle and introduces an 

 error known as the "deviation of the compass." Secondly, it 

 weakens the force of the Earth's magnetic field acting on the 

 compass. Both of these effects vary with place, time, and course 

 of the vessel. A change of cargo, or the buffeting of an iron ship 

 by the waves, will change the "deviation." 



Ordinarily a ship-master has his compass "adjusted" by placing 

 magnets or pieces of iron in the neighborhood of it in such a way 

 as to counteract the effects of the iron ship. But to make this 

 adjustment, he must first know where the compass would point 

 on a non-magnetic vessel like the Carnegie. With this information 



