— 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.