DEPARTMENT OE TERRESTRIAL MAGNETISM. IQQ 



The results were also in excellent agreement witK those derived from the 

 admirable Riicker and Thorpe magnetic survey of the British Isles when 

 referred to present date with the aid of the Falmouth Magnetic Observatory 

 records. The Falmouth Observatory rendered valuable assistance in various 

 ways. 



Both at St. Johns and Falmouth the Carnegie was visited by distinguished 

 persons — men eminent in public affairs as well as in science. Both the 

 Governor and the Premier of Newfoundland made special visits, and at Fal- 

 mouth official visits and inspections were made by Sir Arthur Riicker and 

 Professor Arthur Schuster, both members of the Advisory Council of the 

 Department, as also by Commander Chetwynd, superintendent of the Com- 

 pass Department of the British Admiralty. Special courtesies were extended 

 to the vessel at both ports. As she left St. Johns, messages of farewell and 

 wishing a pleasant voyage were hoisted on H. M. S. Brilliant (Capt. Haworth 

 Booth, in command) and on Cabot Tower on Signal Hill towering above the 

 narrow entrance to the harbor. 



Owing to the great advantage of having a vessel requiring no deviation 

 corrections whatsoever, and because of the perfection reached in the instru- 

 ments themselves, it was possible, for the first time, to make the results 

 known immediately upon conclusion of a voyage. Thus the magnetic data 

 obtained on the trip from Long Island Sound to Falmouth (September i- 

 October i8) were communicated at once to the leading hydrographic estab- 

 lishments of the world, were laid before the Russian Geographic Society at 

 St. Petersburg by General Rykatcheff on October 2y, and were published in 

 Nature on October 28. 



Errors of sufficient importance even to the navigator were found. Along 

 the track followed by the Atlantic liners from England to a point off New- 

 foundland, the present magnetic charts, in general, show too large westerly 

 declination (variation of the compass), the error reaching nearly a degree. 

 Thereafter and continuing to Long Island the charts give systematically too 

 small westerly declination or variation of the compass, by amounts reaching 

 one degree and a half in the maximum. Owing to the peculiar and systematic 

 nature of the errors, their effect is always to set a vessel toward Sable Island 

 or Newfoundland when her course must be shaped entirely by the compass 

 and the log, as is the case in time of fog or cloud. Some of the expert cap- 

 tains of our ocean liners have suspected the possibility of such errors, but the 

 Carnegie has now definitely proved and published the fact and has revealed 

 the cause. 



The chart errors in magnetic dip may amount to one-half degree, and in 

 the horizontal component of the magnetic force the error reaches at times 

 nearly one-tenth part; the chart force values are in general too low by 

 about one forty-fifth part. A part of the errors found in the three magnetic 

 elements are due to secular variation. 



