Editorial Comment. 185 
also maintains that the greatest extension of these glaciers 
was contemporaneous with the Ice age of the northern hemis- 
phere. 
Passing over the ensuing chapters which treat of the move- 
ments of a glacier and of the abrading power of ice, we come 
to the chief assault upon the glacial theory of Agassiz as now 
accepted. All the arguments that have been urged against 
the existence and action of a continental ice-sheet are mar- 
shalled in order and make a formidable showing. The co- 
existence of till and striation, the nature of glacial erratics, 
etc., etc., are brought forward to disprove the occurrence of any 
continental ice-mass. The following chapter is a contention 
that the action of land-ice in the so-called glacial period, as 
in our own time, was limited to ice in the form of glaciers. 
The chapter may fairly be called a very strong presentation of 
the arguments on his side of the question. There is no deny- 
ing or disputing the fact that in the ordinary discussion of 
the subject much of the opposing evidence is left out, glossed 
over, or explained away in a more or less unsatisfactory man- 
ner. A vast amount of work yet remains to be done before 
just views can prevail on this topic — views less icy than those 
of Agassiz, on the one side, and less watery than those of the 
diluvial geologists, on the other. 
The author's expressions thus far have been marked by can- 
dor and fairness. He is a rebel against the strictly uniformi- 
tarian school of geology, and his book is a really valuable rep- 
ertory of facts for reference. It may be considered an 
element in the reaction which has apparently set in against 
extreme views on the glacial catastrophe. It ismarked by 
industry, perseverence and modesty, and may well lead some 
of the extreme glacialists to reflect upon the unremoved diifi- 
culties that 3 T et encumber their path. 
Up to this point we have followed our author with much 
interest and no little pleasure, and we think our readers would 
do the same. But when, in his last chapter, he leaves the re- 
viewing of geological literature and the summing up and 
presentation of evidence, and goes on to develop his special 
theory, to support which is his great aim and effort, we are 
unable to use the same favorable language. Supplemental to 
the local but extensive glaciers, which he allows, he invoke-. 
