RT Journal Article SR Electronic T1 Note on causes of the variations of the magnetic needle JF American Journal of Science JO Am J Sci FD American Journal of Science SP 253 OP 256 DO 10.2475/ajs.s3-42.249.253 VO s3-42 IS 249 A1 Frank H. Bigelow YR 1891 UL http://www.ajsonline.org/content/s3-42/249/253.abstract AB