264 Editorial Commeiit. 
and the imperfection of the geological record is another. The 
latter will never be entirely overcome. •'" * ■' I 
must therefore ask the reader to remember that some of the 
restorations attempted in the following chapters, especially 
those of the earlier periods of geologic history, are built on 
slight foundations and may 1)e modified by the results of new 
discoveries." 
We do not propose to follow in full detail our author through 
the whole field over which he has traveled. Few American 
readers are sufficiently familiar with European geology to be 
interested in them and those to whom the topic is attractive 
will want to accompany him personally without the interven- 
tion of a guide. We shall therefore give only a brief summary 
of his views sufficient to indicate the scope of the book. 
In the present state of our ignorance regarding the Archa-an 
era Mr. Jukes-Browne has done well in giving the merest out- 
line sketch. His representation abounds in shadow}'- forms 
and vague description as the maps of the old geographers who 
supplied their want of knowledge with suiipositions such as, 
^' Hio habitare dicuntur leones'' '' Hie sunt Laiue montes,'' 
etc., etc. No attempt is made to give an map of Archtean Brit- 
ain but we are simply told that a few spots in the north of 
Scotland, the western islands, the northwest of Ireland and 
certain districts in England consist of Archaean rocks. Heevi- 
ently inclines to the belief that many of them are of igneous 
origin. 
In the next or Cambrian era the author agrees witli Mr. 
Callaway that there then existed a mass of land in the North 
Atlantic of which a part of Norway, the Hebrides, Donegal and 
the highlands of Connemara are the worn and inconspicuous 
remains. From this passed continent were derived the sedi- 
ment that built the Cambrian rocks of Europe, then for the 
most part a sea area to the southeast. 
In the Ordovician or Lower Silurian era which followed we 
are for the first time presented with a map. It represents a 
mass of land stretching in from the west and reaching the site 
of Edinburgh with two small islands, one in central England 
and the other between England and Ireland. All the rest of 
the area is occupied by sea. 
The Silurian (Upper Silurian) which follows shows us the 
island in central England still persisting but changed in form, 
