Scoresby_, xlviii, 33. ---- needle, dipping, theory of adjusting, _T. H. Perry_, xxxvii, 277. ---- ----, ----, manipulations of, _J. Locke_, xlii, 235. ---- ----, dip of, see _Magnetic dip_. ---- ----, on the influence of the Aurora on, xxxiv, 285. ---- ----, ibid, _Franklin_, xvi, 148. ---- ----, ibid, _J. Henry_, xxii, 143. ---- ----, ibid, of Jan., 1837, New Haven, xxxii, 179. ---- ----, ibid, in July, 1837, xxxiii, 146. ---- ----, ibid, at Schenectady, Jan., 1837, &c., _B. F. Joslin_, xxxv, 152. ---- ----, ibid, Nov. 14, 1837, _E. C. Herrick_, xxxiv, 269. ---- ----, ibid, xl, 48. ---- ----, ibid, May, 1840, at Toronto, xl, 337. ---- ----, ibid, as seen at Greenwich, xl, 338. ---- ----, influence of coasts on the deflection of, xxviii, 62. ---- ----, ---- of heating to the temperature of boiling water, xxxviii, 180. ---- ----, influence of iron cooled to a low red heat, xxix, 348. ---- ----, improvement in the manufacture of, _A. Eaton_, xii, 14. ---- ----, improvement in, reply to the same, xii, 232. ---- ----, made of thin plates not in contact, _W. Scoresby_, xxxiv, 398. ---- ----, oscillations of, differing near different metals, xv, 182. ---- ----, polarity and dip of, a remark on, xxix, 353. ---- ----, made to indicate the true north, xxvi, 90. ---- ----, on the connexion of the theory of the earth with the secular variations of, _J. H. Lathrop_, xxxviii, 68. ---- needles, best position of three, for mutual action, _H. Lloyd_, xxxviii, 96. ---- observations, a union of effort urged for carrying on, xviii, 380. ---- ----, great scheme for, by the Royal Society of London, xxxvii, 198. ---- ----, ibid, by British Association, xl, 335; xlii, 151; xliii, 374. ---- ----, in Russia and other countries, in progress, xlii, 153. ---- ----, coöperation of the Amer. Acad. of Arts and Sciences in a general system of, xxxix, 193. ---- ----, corresponding, by _A. D. Bache_ and _H. Lloyd_, xli, 260. ---- observatory at Dublin, xxxiv, 3. ---- poles, revolution of the two, xxix, 352. ---- polarity, notice of, _D. H. Barnes_, xiii, 70. ---- ----, reply to _D. H. Barnes_, xiv, 121. ---- ---- of rocks, xx, 198. ---- power of a galvanic battery, v, 388. ---- separating machine for magnetic ores of iron, used at Franconia, xviii, 289. ---- variation, daily, different in different places, xix, 189. ---- ----, at Perth, Scotland, xl, 342. ---- ----, at Paris, France, xxxi, 190. ---- ----, remarks on, _N. Bowditch_, xvi, 64. ---- ----, for the United States, _E. Loomis_, xxxiv, 290^f; xxxix, 41^f; xliii, 106. ---- ----, table made from observations at Boston, Falmouth and Penobscot, xvi, 60. ---- ----, at Providence, R. I., _M. B. Lockwood_, xliv, 314. ---- ----, at Troy, N. Y., xvii, 198. ---- ----, in some parts of New York State, xxxvi, 28. ---- ----, in Connecticut, _G. Gillet_, xxiii, 205. ---- ----, at Yale College, xxx, 221.