342 Rfvieiv of Becoit Geological Literature. 
principal ocean currents and isothermal lines of January and July and the 
mean annual line of 32 degrees Fahrenheit in both hemispheres. There 
are also three plates of sections: — 1. Illustrating the action of springs and 
underground waters (several sections in England). 3. Coal fields of 
Somerset and Bristol, of Liege, and of AVestphalia. o. The Mount St. 
Gothard tunnel, i>art of the northern Hanks of the Alps, and across the 
Alps from the neighborhood of Zurich to near Como, i;iO miles. Two 
chapters, pp. 308-359 are devoted to metalliferous deposits. Igneous 
rocks are the theme of the next two chapters, pp. 360-396; and the last 
three chapters, pp. 397-450, treat of metamorphism and the metaraorphic 
rocks. 
Facing the first page of volume ii is a geological map of Europe on a 
scale of 150 miles to an inch, executed, under the author's direction, by 
William Topley, F. G. S., and J. G. Goodchild,|F. G. S., from the latest sur- 
veys. This is a very detailed and valuable map, well printed and colored, 
the colors being mainly those proposed by the International Geological 
Congress. A second map in this volume, uniform with those of volume 
i,shows the probable extent of land covered by ice and snow during the gla- 
cial periodjtheir extent now,and the present boundaries of fioating ice. In 
the first chapter, pages 6-18 contain a table of the sedimentary strata in 
England and their correlation with some of the principal continental groups, 
and lists of the formations in India, North America, Australia, New 
Zealann!, and South Africa, each of these lists being annoted with some of 
the characteristic genera of the flora and fauna. The second chapter 
pp. 19-29, treats of the Archwan rocks. Twenty-five chapters, pp. 30- 
440, give the history of the Pala?ozoic, Mesozoic, and Kainozoic eras, 
and describe their groups of rocks and fossils. Six chapters, pp. 441- 
535, relate to the Quaternary period. The two concluding chapters are 
entitled respectively, "Theorvtical questions: condition of the earth's 
crust" (pp. 536-549), and "The primitive state of the earth" (pp. 550-563). 
Besides the maps mentioned, volume ii is illustrated by sixteen plates 
of fossils, and about 270 well executed wood-cuts, many of them com- 
prising separate figures of several species of fossils. Each volume has 
an ample iniex. 
Treating of the condition of the earth's mass, the author decides that 
the hypothesis most compatible with the geological phenomena is that of 
a central solid nucleus, surrounded by a molten yielding envelope, not fluid 
but viscid or plastic, measured in thickness not by hundreds, but by tens 
of miles, Avhile the external solid crust of the earth, so far as geological 
observations indicate, need not have a thickness of even twenty miles. 
But the deposition of sediments in great thickness is believed by professor 
Prestwich to be nota cause, but a result, of continuea submergence of 
their area. He concludes that the earth's crust has become more stable 
with the progress of the geologic Hges, this condition being most marked 
during the time since the glacial period, so that now the manifestation of 
its mobility is on a comparatively small scale and in general of extreme 
slowness, adapting the earth for the habitation of civilized man. Aero- 
lites are considered to be probably fragments of asteroids, affording there- 
