_Sibbald, R._, notice of, with an enumeration of his works, xxxvii, 138. Siberia, steppes, xvii, 23. ----, depth of the frozen ground in, xxxvi, 210. ----, temperature of the ground in, xxxvi, 205. ----, notice of Humboldt's expedition to, xvii, 405. Siberian elm, notice of, xx, 377. _Sibley, J._, fact from a letter by, relating to the Texas meteoric iron, viii, 221. Sicily, earthquakes of 1823, ix, 216. ----, geological structure of, _F. Ferrara_, viii, 201. ----, marbles of, viii, 203. ----, minerals of, viii, 203. ----, geology of, _C. Daubeny_, x, 230.^f ----, volcanic character of, xiii, 272. ----, fountain of Cyana in, xxvii, 82. Sida abutilon, affording a material for cordage, xxi, 37. Sidero-graphite, _J. Torrey_, ii, 176, 370. Sideroscope, xv, 177. _Siebold's_ Flora Japonica, noticed, xxxix, 175. Sienite, see _Syenite_. Sigillaria, generic characters, vii, 180. ---- marineria, xxxi, 30.^f ---- in the coal fields near Liverpool, xlv, 403. ----, remarks on the relation of, to Stigmariæ, xlix, 227. Signals, iii, 382. ----, telegraphic, by rockets, v, 189. Signs, observations on the language of, viii, 348. Silene axillaris, vii, 62. ---- regia, xi, 182. Silex, fusion of, ii, 292. ----, solubility of, xiv, 385; xli, 60. ----, gelatinous, _Guillemin_, xiv, 391. ----, in solution, in geodes, viii, 282. ----, ----, ibid, _G. Bischof_, xlix, 396. ----, hydrate of, xv, 390. ---- in plants, xxxiv, 27. Siliceous buhr millstone deposits of Ohio, xxix, 142. ---- ----, hot water origin, xxix, 45. ---- minerals, on the treatment of, by carbonated alkalies, xviii, 404. ---- ----, solution of, by steam, xlviii, 397. ---- glass from burning hay, xix, 395; xxiv, 174. ---- corals, i, 141. ---- shells, corals and wood of Antigua, _S. Hovey_, xxxv, 79; --due to siliceous solutions, 82. ---- Sinter of the Azores, _J. W. Webster_, iii, 391. ---- springs and deposits in India, _Newbold_, xlix, 398. ---- substances, porosity of, vii, 192. ---- ----, containing siliceous infusoria and minute organic remains, _Turpin_, xxxii, 400. Silicic acid, see _Silex_. ---- ether, _Ebelman_, xlix, 192. Silicification of fossils, proceeding from thermal springs in Florida, _C. U. Shepard_, xxv, 165. ---- of wood, xxxiii, 108. ----, remarks on, _J. D. Dana_, xlviii, 88, 397; xlix, 227. Silicified wood, see _Fossil_. Silicon, how obtained, ix, 377. ----, a process for obtaining, _R. Hare_, xxii, 189; xxiv, 247^f; xl, 28. ----, production of, from paracyanogen, _S. M. Brown_, xli, 208. ----, on the alleged conversion of carbon into, xlii, 193. Silk, on the manufacture of, in America, xviii, 382; xix, 175. ----, review of F. Pascalis on the culture of, xvii, 202; xviii, 278. ----, practical instruction concerning, xviii, 207, 278. ----, on the culture of, in India, xl, 39. ----, grown at Nottingham, England, xxxviii, 130.