Peat, on the use and mode of formation of, _E. North_, xi, 67. ----, on the origin, preparation and uses of, from a memoir by _Ribaucourt_, xv, 250. ----, gas light from, xxx, 189. ----, instance of bituminization of, in Maine, _C. T. Jackson_, xxxiv, 73. ----, in Massachusetts, xxii, 38. ----, in New York, i, 139; v, 8; xxxvi, 16. ----, moss, mode of determination of age of, xxix, 349. Peat-bogs, observations on, _G. H. Adams_, xxxviii, 127. _Peck, J._, geology of the mining districts in Georgia, western North Carolina and East Tennessee, with a map, xxiii, 1. Pecten, uses and economical notice of, xxxii, 248, 219. Pectic acid, converted to oxalic, xvii, 179. _Peirce, B._, elements of the third comet of 1845, xlix, 220. _Peligot, E._, on tea, xlviii, 187. _Pelletier_, on guaiac resin, xlix, 194. Peloconite, new mineral species, xxii, 387; xxvi, 386. Pelopium, new metal, xlviii, 400. _Pelouze, J._, on tannin, xxviii, 124. ----, on the atomic weights of simple bodies, xlvii, 188. ----, on the solubility of chlorine in water, xlvii, 191. _Peltier_, on tornadoes, xxxviii, 401. Pendulum, new compensating, _W. G. Jones_, xxxviii, 274.^f ----, experiments on the vibrations of, with different suspending springs, _W. J. Frodsham_, xxxvii, 278. ----, _W. J. Frodsham's_ improved compound, xxviii, 107. ----, portable mercurial, _E. J. Dent_, xxxv, 289. ----, vibrations of a mercurial, _G. Baker_, xlviii, 156. ----, barometric compensation of, xlvi, 393. ----, oscillations in the plane of the meridian and at right angles with the same, different, xxviii, 62. ----, simultaneous motions of the surrounding air and, _S. D. Poisson_, xxiii, 391. ----, _E. Sabine's_ experiments with, and conclusions, xvii, 364. ----, on the reduction to a vacuum of the vibrations of an invariable, xvii, 365. Penetrativeness of fluids, xix, 360. Penguins, habits of, xlix, 151. _Pennant, Thos._, life and writings of, xxxvii, 146. Pennatule flèche, iv, 87.^f Pennine, form and analysis of, xlvii, 216.