454 



FAI'F.IUTION TO POINT BA11ROW, ALASKA. 



tinii observations will be made every 'JO seconds, beginning with the full hour and minute of Got- 

 tingen niean civil time. 



"If three observers are available, all three instruments Avill be observed. 



"Absolute magnetic measures of declination, dip. and intensity. Observations are to be made 

 as often as necessary to furnish the absolute values needed for the differential measures. [Unless 

 some change is suspected in the latter, it will suffice to observe for absolute values the declination, 

 the dip. and the horizontal intensity (oscillations and deflections) on the day before each term-day. 

 Declination observations will then be made about 8 a. m. and 1 p. m., local time, and for those and 

 the intermediate hours the corresponding readings of the scales of the differential and absolute 

 instruments will be given. Observations for dip and intensity may be made at any convenient 

 time of the day. Sch.j 



"Tests are to be made for possible local deflection before selecting the position for the abso- 

 lute instruments. 



Sriilf valves of differential instruments. The unifllar or declinometer should have a sensi- 

 tiveness such that 1 millimeter on the scale will correspond to a variation in declination (J)) equal 

 to 1', hence f>D=l'. For the bifllar or horizontal force magnetometer at a place where the dip is o, 

 1 millimeter of its scale will be made to correspond to a variation of the horizontal component (H) 

 of the magnetic force equal to 0.001 cos 0, hence lf=.001 cos o expressed in the metric units of 

 the force nun. m</, s. For the vertical force or balance magnetometer, 1 millimeter of the scale 

 will be made to correspond to a variation of the vertical component (V) of the force =0.001, 

 hence -7T r =.001 in the same units as above."** 



For absolute measures the Point Barrow party had Coast and Geodetic Survey magnetometer 

 No. 11. and the Lady Franklin Bay party magnetometer No. 12, both new instruments, made by 

 Fauth & Co., of Washington. Kew dip circle No. 23 was taken to the former place, and Kew dip 

 circle No. 1!) to the latter, both instruments the property of the Coast and Geodetic- Survey. The 

 magnetometers are described and figured (Plate No. 36) in Coast and Geodetic Report for 1SS1, 

 Appendix Xo. 8. The Kew dip and intensity circles with needles centimeters in length are well 

 known. 



tiKOCUAPMK'AI. POSITION OF 1<J J.AAMIK STATION, ALASKA. 



The two United States Polar expeditions which had been organized under the orders of \V. 

 B. llaxen, brigadier and brevet major general, U. S. A., and Chief Signal Officer, left for their 

 respective destinations early in the summer of 1881, the one for Alaska in command of I'. II. Kay, 

 lieutenant, IT. S. A., the other for Lady Franklin Bay in command of A. YV. Greely. lieutenant, 

 U. S. A. 



, fur tin' sak.' <if illustration, tliat .'H Point Harrow //--O. '..". on mm. mi/. . units' :inil " -H-, 



\vr havr lo^ cot : '.i.T'.'H'i-J. hem -r ill .VJ ! anil 



cos'/ .117" and O'//--.IMKH 17" ._'. nearly. From col _'= . - f>H 



i;7tn; H H,-'- i 



tin 1 whole aiifjlc to lie turiii-d oil would In- '.1(1 -)-.- l.'.l "iii . Kor Hie- \crlir:il force instrument we have from 

 / // tan 'J, I' t;.:i.Vi.-): also, total lorce /' //serf) li. |-.'7-J and for .1 I .Ol)l (metric nnitsi. '"" ' .Miinir,:;! The 

 un;;iilar value of one division of each of the sc.tles <t<|ii:i!s I . 



