THE EARTH S MAGNETISM — BAUER. 199 



We find Halley embracing every occasion — 



to recommend to all Masters of Ships and all others, Lovers of Natural Truths, 

 that they use their utmost Diligence to make, or procure to be made, Observa- 

 tions of these Variations in all parts of the World, and that they please to com- 

 municate them to the Royal Society in order to leave as compleat a History as 

 may be to those that are hereafter to compare all together and to compleat and 

 perfect this abstruse Theory. 



Consulting the minutes of the Royal Society, it is found that 

 Halley communicated, from time to time, the results of magnetic 

 observations received from various expeditions, as also the values 

 of the magnetic declination observed by himself, at London, viz : 



1701. May 7. — Mr. Halley tried the experiment of the Variation of the Needle 

 this day with the two needles he had with him in his late, Voyage; and by the 

 one the Variation was 7° 40' ; by the other, 8° 00' W. 



1702, July 8. — Mr. Halley observed the Variation of the Needle, which was 

 found to be Si° Westward, or very near it. 



1716, May 24. — Dr. Halley rejiorted that he had drawn a Meridian Line on the 

 stone erected in the Society's yard before the repo.sitory and that the Variation 

 was found at present to be full twelve degrees. 



These observations of the magnetic declination of 1701, 1702, and 

 1716 are perhaps printed here for the first time and are not found 

 in any of the compilations of magnetic declinations at London pub- 

 lished thus far. Only Halley's earlier observations, namely, those 

 of 1672 (2° 30' W.), 1683 (4° 30' W.), and of 1692 (6° 00' W.), hav- 

 ing been given by Halley himself in his printed papers of 1683 and 

 1692, have become known to compilers. 



CHANGE OF THE MAGNETIC DECLINATION IN THE ATLANTIC OCEAN 

 SINCE HALLEY'S CHART. 



In view of the fact that the two vessels — the Paramour Pink and 

 the Carnegie — both being primarily dependent for theii^ motive 

 power upon the prevailing winds in the Atlantic Ocean, have fol- 

 lowed nearly identical courses, it will be a matter of no little inter- 

 est to compare the values of the magnetic declination given on Hal- 

 ley's chart for 1700 with those obtained by the Carnegie in her 

 cruises in 1909-10, We find first that over the entire Atlantic, from 

 50° N. to 40° S., the north end of the compass needle in 1910 was to 

 the west of the compass direction of 1700 by amounts varying with 

 locality. Thus for various important ports the approximate change 

 was as follows: New York, 2°.9 W. ; St. Johns, Newfoundland, 14°.6 

 W.; Falmouth, England, 10°.4 W.: Funchal, Madeira, 15°.6 W.; 

 Bermuda, 10°.5 W.; Porto Rico, 7°.6 W.; Para, Brazil, 14°.6 W.; 

 Rio de Janeiro, 20°.8 W.; Buenos Aires, 13°.0 W.; Cape Town, 

 16°.2 W. 



