BOOK REVIEWS 533 
ern volcanoes of Iceland is introduced by way of illustration. ‘The 
eruptive vents and the intrusive bodies, as sills and bases, both basic 
and acid, are also described. 
The work closes with an account of the subsidences and disloca- 
tions of the plateaux and the effect of denudations. ‘The final chapter 
consists of a brief summary together with the following general deduc- 
tions: The distribution of the centers of volcanic activity has been along 
the western side of the country in a north and south line. ‘The per- 
sistency of volcanic activity in this region and its restriction to particu- 
lar localities are some of its most marked features. ‘The sites of volcanic 
vents in Britain do not seem to have been determined by any obvious 
structures in the rocks now visible. Volcanic phenomena cannot be 
regarded as mere isolated and incidental features in the physics of the 
globe. ‘They are intimately connected with profound terrestrial move- 
ments. They have been essentially uniform since the beginnings of 
geological time. In extent and rigor the earliest eruptions of which 
we have records did not differ in any important respect from those of 
the present time. However volcanic energy has not manifested itself 
uniformly throughout geological time. There have been periods of 
maximum and of minimum effectiveness. The character of the vol- 
canic rocks and the general sequence of their eruption have been the 
same with slight modification for all the periods of activity in this 
region. Jo- Pp DINes; 
The Submerged Valleys of the Coast of Califorma, U. S. A., and of 
Lower California, Mexico. GEORGE Davipson, A.M., Pu.D., 
Sc.D. (Member of the National Academy of Sciences, 
etc) coc. Calinncad «Scr, Vhird Semes, Geology, Vol: 1, 
No. 2. With Nine Plates. San Francisco, 1897. 
This paper gives a brief description of the Pacific coast from the 
southern extremity of Lower California to the Strait of Fuca. The 
general character of the coast, south of Cape Mendocino, is bold and 
rocky, reaching considerable elevations within a few miles of the shore. 
These coastal ranges are broken by valleys and plains of varying width 
which may or may not correspond to the submarine depressions des- 
cribed. 
Bordering the coast from about Cape Mendocino southward there is 
generally a submarine platform, having an average width of ten miles, 
