COMMITTEES ON BEHALF OF THE GOVERNMENT 217 



was all of rope, of others part iron and part rope, and still others, 

 all iron. The decks of wooden vessels were also often of iron. 



Vessels at this time appear to have carried several compasses 

 which were sometimes arranged in pairs, and were placed in 

 what were thought to be the most convenient locations. The 

 presence of large masses of iron, often within a few feet of 

 the compasses caused a large and variable amount of deviation 

 on which account navigation was at times extremely precarious. 

 Various plans had been proposed from time to time for overcom- 

 ing the local attraction, some of which seem strange indeed, such 

 as setting the compasses in iron pots four inches thick, placing 

 them in zinc cases packed with charcoal, etc. The method which 

 seems to have been most effective was the one invented by the 

 English astronomer Airy, which consists in counteracting the 

 local attraction by means of bar magnets placed in suitable loca- 

 tions. The committee of the Academy adopted this method for 

 the war vessels which they inspected, making use of the services 

 of an expert, A. D. Frye, of New York, to carry it into practical 

 efifect. They supervised the correction of the compasses on 27 

 vessels of all kinds, including sloops, monitors, gunboats, pro- 

 pellers, side-wheel steamers, tugs and transports, and were 

 occupied in the task from March until late in September. Some 

 of the vessels were at New York, others at Boston, Philadelphia, 

 and Hampton Roads. At Philadelphia a compass station had 

 not been established, and at the request of the Bureau of Naviga- 

 tion, one member of the committee, Fairman Rogers, gave 

 personal attention to the ship Ticonderoga, which was lying 

 there, and made a special report to the committee. 



In addition, Charles A. Schott and G. W. Dean, assistants in 

 the U. S. Coast Survey, made, by direction of Professor Bache, 

 an extended series of magnetic observations on the first-rate iron- 

 clad Roanoke and the monitor Passaic at the Brooklyn Navy 

 Yard, and also some experiments in the iron-clad Monadnock 

 at the Charlestown Navy Yard. 



