844 Notices respecting New Books: — Darwin on the 



localities is distributed, as well as of its nature, the following " con- 

 tents" of the first and last chapters will give a sufficient notion, 



" Chap. I. — St. Jago, in the Cape de Verde Archipelago. — Rocks of the 

 lowest series — A calcareous sedimentary deposit, with recent shells, altered 

 by the contact of superincumbent lava, its horizontality and extent — Sub- 

 sequent volcanic eruptions, associated with calcareous matter in an earthy 

 and fibrous form, and often enclosed within the separate cell* of the scoriae 

 — Ancient and obliterated orifices of eruption of small size — Difficulty of 

 tracing over a bare [)lain recent streams of lava— Inland hills of more an- 

 cient volcanic rock — Decomposed olivine in large masses — Felspathic 

 rocks beneath the upper crystalline basaltic strata — Uniform structure and 

 form of the more ancient volcanic hills — Form of the valleys near the coast 

 — Conglomerate now forming on the sea beach. 



" Chap. VII. — New South Wales — Sandstone formation — Imbedded 

 pseudo-fragments of shale— Stratification — Current-cleavage^Great val- 

 leys — Van Diemen's Land — Palaeozoic formation— Newer formation with 

 volcanic rocks — Travertin with leaves of extinct plants — Elevation of the 

 land — New Zealand — King George s Sound — Superficial ferruginous beds 

 — Superficial calcareous deposit, with casts of branches; its origin from 

 drifted particles of shells and corals; its extent — Cape of Good Hope — 

 Jimction of the granite and clay-slate — Sandstone formation." 



From the second chapter* we extract the subjoined description of 

 the island called St. Paul's Hocks, including that of a glossy incrus- 

 tation coating extensive portions of those rocks, which affords an 

 example of the particular class of geological dynamic agents, which 

 Mr. Darwin, as we have observed, has been so happy in recognising 

 in their full importance. 



" St. PauPs Rocks. — This small island is situated in the Atlantic Ocean, 

 nearly one degree north of the equator, and 540 miles distant from South 

 America, in 29° 13' west longitude. Its highest point is scarcely fifty feet 

 aDove the level of the sea; its outline is irregular, and its entire circumfe- 

 rence barely three-quarters of a mile. This little point of rock rises 

 abruptly out of the ocean ; and except on its western side, soundings were 

 not obtained, even at the short distance of a quarter of a mile from its 

 shore. It is not of volcanic origin; and this circumstance, which is the 

 most remarkable point in its history (as will hereafter be referred tof), 

 properly ought to exclude it from the present volume. It is composed of 

 rocks unlike any which I have met with, and which I cannot characterize 

 by any name, and nuist therefore describe. 



"The simplest, and one of the most abundant kinds, is a very compact, 

 heavy, greenish-black rock, having an angular, irregular fracture, with some 

 points just hard enough to scratch glass, and infusible. This variety passes 

 into others of paler green tints, less hard, but with a more crystalline frac- 

 ture, and translucent on their edges; and these are fusible into a green 



* A portion of this chapter relates to the effects of steam on the vol- 

 canic rocks of Terceira in the Azores, in which the author observed small 

 aggregations of hyalite that had been deposited by the steam. Dr. Dau- 

 beny had previously observed the same fact in Hungary, and a similar one 

 in Ischia, as noticed in his work on volcanos, pp. 100, 182. 



f This island is afterwards pointed out, p. 125, as one of the very few 

 exceptions to the rule, that all the islands scattered throughout the Atlan- 

 tic (as well as the Pacific and Indian oceans;, arc composed either of vol- 

 canic or of modern coral-rocks. 



