D O C U M E N T 2 9 8 A U G U S T 1 9 2 4 4 6 5 publication of such a paper. If it has been published, will you kindly give me the reference, or if possible send me a reprint? I still recall with much pleasure the very delightful conferences which I had with you at Princeton in 1921 on questions relating to the general theory of relativity and terrestrial magnetism.[6] I hope that if you find it possible to do so you will send me reprints of the papers which you may publish from time to time in journals or in the proceedings of academies. For example, the papers which you presented before the Academy of Berlin and published in the Sitzungsberichte (Phys.-math. K1. Feb. 15, 1923, pages 32–38 and Dec. 13, 1923, pages 359–364) would be of interest to us.[7] One of the interesting results of the analysis of the Earth’s magnetic field for 1922 was the deduction with reference to the non-potential portion which consti- tutes about 3% of the Earth’s total magnetic field (see papers Nos. 1 and 3, men- tioned above),[8] for which we are endeavoring to find some adequate theoretical explanation. At the British Geophysical meeting on March 5, 1923 Sir Arthur Schuster raised a very interesting point (see also page 27 of my paper No. 1), name- ly, “that he did not know that any one had verified that the magnetic force was ac- curately at right angles to the current which produced it.” He said further that he had “very recently met the statement that, according to Einstein’s theory, the force and the current should not be exactly at right angles.” Have you published such a statement and if so where? (If according to the general relativity theory the mag- netic vector should not be accurately at right angles to the electric current, what is the formula for the angle of departure of the vector from perpendicularity?) You will see from the inclosed paper by Mr. Peters of my staff that we have in- vestigated the question of the existence of a non-potential portion of the Earth’s magnetic field by constructing paths which should always be at right angles to the direction of the compass needle.[9] You will see further that the departure from per- pendicularity of the magnetic vector would seemingly be in opposite directions in the two hemispheres. I had found (Par. 14, page 12, my paper, No. 1) that on the average between 5º and 45º North the north end of the compass needle pointed ap- proximately 0º.1 east of north and for the corresponding region in the south hemi- sphere about 0º.1 west of north. Do you think that these observational facts can be harmonized with results from the general relativity theory? With kindest regards and best wishes, as also to your good wife, in which Mrs. Bauer joins me, and hoping to hear from you soon, I remain Very sincerely yours, Louis A Bauer. TLS. [6 069]. Written on letterhead of Carnegie Institution of Washington, Department of Research in Terrestrial Magnetism, and addressed “Prof. Albert Einstein, Universität Berlin, Berlin, Germany.” [1]Bauer (1865–1932) was lecturer on terrestrial magnetism at Johns Hopkins University, and director of the Department of Research in Terrestrial Magnetism at the Carnegie Institution in Washington.