. The semi-centennial anniversary of the National Academy of Sciences, 1863-1913 . h those of a magnetized sphere, and alsothat the magnetic poles coincide with the poles of rotation, itis possible to calculate what the relative displacement shouldbe at different solar latitudes. These theoretical displacementsare shown graphically by the sine curve on the screen (Fig. 15). We see from the curve that the greatest displacements shouldbe found at 45° north and south latitude, and that from thesepoints they should decrease toward zero at the equator and thepoles. Furthermore, the curve shows that
. The semi-centennial anniversary of the National Academy of Sciences, 1863-1913 . h those of a magnetized sphere, and alsothat the magnetic poles coincide with the poles of rotation, itis possible to calculate what the relative displacement shouldbe at different solar latitudes. These theoretical displacementsare shown graphically by the sine curve on the screen (Fig. 15). We see from the curve that the greatest displacements shouldbe found at 45° north and south latitude, and that from thesepoints they should decrease toward zero at the equator and thepoles. Furthermore, the curve shows that we may apply thesame crucial test used in the case of sun-spots: the direction ofthe displacements, toward red or violet, should be reversed inthe northern and southern hemispheres. I shall not trouble you with the details of the hundreds ofphotographs and the thousands of measures which have beenmade by my colleagues and myself during the past year. Inview of the diffuse character of the solar lines under such highdispersion, and the exceedingly small displacements Fig. 13. 150-FOOT Tower Telescope. THE SEMI-CENTENNIAL ANNIVERSARY 51 the results must be given with some reserve, though they appearto leave no doubt as to the reality of the effect. Observations inthe second order spectrum failed to give satisfactory indicationsof the field. But vv^ith the higher dispersion of the third order,eleven independent determinations, made with every possibleprecaution to eliminate bias, show opposite displacements inthe northern and southern hemispheres, decreasing in magnitudefrom about 45° north and south latitude to the equator. Threeof these determinations were pushed as close to the poles as con-ditions would permit, and the observed displacements may becompared with the theoretical curve (Fig. 15). In view of thevery small magnitude of the displacements, which never Angstroms, the agreement is quite as satisfactory as onecould expect for a first approxima
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectscience, bookyear1913
