_Percival, J. G._, minerals of Berlin, v, 42.^f ----, analysis of _Ad. Brongniart_ on fossil vegetation, vii, 178. ----, on the geology and mineralogy of Sicily, viii, 201. ----, on the zoological characters of formations, viii, 213. ----, curious effect of solar light, xii, 169, 180. ----, Report on the Geology of Connecticut, notice of, xliv, 187. ----, crescent form of dikes first observed by, xlvi, 205. Percussion powder, xviii, 156. _Perdicaris, G. A._, on the revival of letters in Greece, xxxvi, 192. _Perkins, G. R._, interesting properties of numbers, xl, 112. ----, solution of a functional equation, xlii, 69. ----, new method of computing interest, xlvii, 51. _Perkins, H. C._, notices of fossil bones from Oregon, xlii, 136.^f _Perkins, J._, compressibility of water, iii, 347.^f ----, engraving on steel, iii, 353. ----, new steam engine, vii, 111.^f ----, mode of applying his method of generating steam to the boilers of ordinary steam engines, vii, 116, 332.^f ----, on steam engines, xiii, 40. ----, on the cutting of steel by soft iron, vii, 390. _Perkins, T._, salting of ship timber, ii, 117. _Perkins's_ Algebra, noticed, xliii, 380. _Peron_, on the temperature of the ocean, xvii, 295. _Perrine, H._, on the Agave and other plants used for cordage, xxv, 330. _Perry, T. H._, magnetic dip in different regions, xlvii, 84. ----, method of adjusting the dipping needle, xxxvii, 277. ----, on some of the probable effects of a resisting medium, xxxviii, 246. _Persoon_, obituary notice of, xxxii, 215. Peru, Andes of, xviii, 182. ----, ----, highest elevations of, xviii, 184. ----, ----, highest habitations of men in, xviii, 183. ----, ----, trachytes of, xviii, 183. ----, ----, the mining regions of, xvii, 43. ----, mines of, xvii, 43^f; xxiv, 232. ----, physical features, xvii, 47. ----, antiquities of, xvii, 116.^f ----, ancient and modern races of, _S. G. Morton_, xxxviii, 360^f, 365.^f ----, ancient race of men in the Andes, xxix, 358. ----, Atacama, nitrate of soda of, xii, 385. ----, province of Tarapaca, _J. H. Blake_, xxxix, 375; xliv, 1.^f Peruvian bark, on, _G. W. Carpenter_, ix, 363; xvi, 28. ---- ----, on a new variety of, _G. W. Carpenter_, xx, 52. ---- ----, adulterations in, xix, 81. _Pestalozzi, H._, death of, xiii, 183. Pestalozzian system, ix, 163; x, 145. Pestum, stone of the temples at, xxxvii, 366. Petalite in Canada, viii, 69. Petersburg, St., Russia, libraries of, v, 177. ----, Botanic Garden, xx, 175. Petrified, see _Fossil_. Petrifying springs in New York, xxxvi, 11. Petroleum in the salt springs of the Ohio valley, xxiv, 63. ---- in the valley of the little Kenawha, xxix, 86. ---- in the Kenawha valley, xxix, 121. ---- in the valley of the Sandy river, Virginia, xxix, 129. ---- or oil spring of Allegany Co., N. Y., xxiii, 97. ----, well of, near Burksville, Ky., xxxix, 195.