INDEX. 
Secondary rocks, volcanic, of many different 
ages, 335 
Secondary fresh-water deposits why rare, 
330 ' 
Secondary periods, duration of, 328 
Sedgwick, Professor, on diluvial waves, 
101, 272 
on the tertiary formations of Styria, 
213, 214 
- on the volcanic rocks of Styria, 224 
on the Isle of Wight, 281, 315 
on synclinal lines, 293 
— — on the theory of M. Elie de Beau- 
mont, 347 
on the Cornish granite veins, 355 
on garnets in altered shale, 369 
Sediment, changes in the distribution of, 
which would take place on the filling up 
of large lakes, 27 
Sedimentary deposition, causes which oc- 
casion the shifting of the areas of, 26 
Sedimentary rocks, distinction between 
volcanic and, 10 
Seguinat, Montague de, lamination of 
clay-slate in the — see wood-cut, No. 89, 
366 
Selenite found in clay at the foot of Etna, 77 
Septaria of the London clay described, 279 
Serre del Solfizio, sections of buried cones 
in the cliffs of, 88 
dikes at the base of — see wood-cut 
No. 19, 90 
Serres, M. Marcel de, on the drifting of 
land shells to the sea by the Rhone, 48 
on the tertiary strata of Montpellier, 
215 
— — on the fossil insects of Aix, 277 
Sicily, geological structure of, 22, 63 
dip and direction of the newer Plio- 
cene strata of, 73 
■ origin of the newer Pliocene strata 
of, 103 
form of the valleys of, 109 
no peculiar indigenous species found 
in, 115 
■ ■ breccias containing bones of extinct 
animals in caves in, 139 
— — alluviums of the newer Pliocene, 
period in, 151 
fossil shells of — see Tables, Appen- 
dix 1. 
— — number of living species in the fos- 
sil shells of — see Appendix I., 47 
— — • number common to Italy and, ib. 47 
■ number common to Italy, the Crag 
and, ib. 47 
number of species proper to, ib. 47 
Shells, tables of fossil — (see Appendix,) 49 
characteristic tertiary — (see Plates,) 
50 
— — — necessity of accurately determining 
the species of, 50 
Shells, recent, numerical proportion of in 
the different tertiary periods, 58 
number of species of, found both 
living and fossil, 394 
fossil tertiary, number examined to 
construct the tables, 394 
fossil, number common to all the 
tertiary periods, Appendix I., 50 
living, number of those found in a fos- 
sil state in all the tertiary periods, ib. 50 
geographical distribution of those 
species which have their fossil analogues, 
ib. 51 
Sherringham, sections in the cliffs east of 
— see wood-cuts, Nos. 39 and 40, 178, 
179 
rapid waste of the cliffs at — see sec- 
tion, wood-cut No. 72, 297 
Shetland, action of the sea on the coast of, 
146 
granites of different ages in, 357 
— — passage of trap into granite in, 362 
Siebengebirge, volcanic phenomena of the, 
198 
Sienna, Subapennine strata near the town 
of, 160 
microscopic fossil shells very abun- 
dant near, 163 
■ list of fossil shells from — Appendix 
II., 59 
Siliceous schist, clay converted into by 
lava, 70, 81 
Silvertop, Col., on the tertiary strata of 
Spain, 170 
Simeto, plain of the, 76 
Sioule, river, ravines cut through lava-cur- 
rents by the, 265 
Sky, age of the granite of, 358 
Smyth, Capt. W. H., his drawing of the 
Isle of Cyclops — see wood-cut No, 14, 
on the extinct volcanos of Sardi- 
nia, 193 
Somma, escarpment of, 84, 85, 87, 96 
changes caused by dikes in the, 91 
dikes of, 121 
minerals found in, 121 
i parallelism of the opposite sides of 
the dikes of, 122 
varieties in the texture of the dikes 
of, 124 
Somma and Vesuvius, differences in the 
composition of, 120 
Sortino, great limestone formation seen in 
the valleys of, 64 
bones of extinct animals in caves 
near, 139 
South Downs, chalk ridge called the, 287 
section from to the North Downs 
across the Weald Valley — see wood-cuts 
No. 63 and 64, 288 
highest point of the, 288 
