1880.] 483 [Crosby. 
less typical developments of the Laurentian, Huronian, Montalban, 
and Taconian; while in the British Isles the correspondence seems 
well nigh perfect, and we are able to find there nearly everything 
observed on this side of the Atlantic, from the lowest Laurentian to 
the base of the Cambrian. 
Dr. Hunt’s most recent and, in some respects, most important con- 
tribution to the literature of this subject, is a paper read before the 
American Association for the Advancement of Science in September 
last, and published in the current number (April, 1880) of the Amer- 
ican Journal of Science. In this we have: 1. An introduction, in 
which are indicated the main points of difference between what may 
be styled the plutonic and metamorphic schools of geologists, con- 
cerning the origin of the stratified crystallines, with a concise state- 
ment of the creed of the new school, of which Dr. Hunt may be 
fairly called the founder. 2. A brief historical sketch of the prog- 
ress of our knowledge of the crystallines of North America during 
the last sixty years, with some of the more important correlations of 
the rocks of this country with those of Europe. 38. An account of the 
recent investigations in this department of geology in Great Britain, 
including a statement of the author’s latest views concerning the age 
of the pre-Cambrian rocks of that country, and a partial list of the 
publications relating to them, which must prove very useful to the 
student. 
Although the comparisons so far made between this country and 
Kurope have not been exhaustive, yet, in the writer’s opinion, enough 
has been done to show that, considering their age and the distance 
which separates them, the older rocks of the two continents exhibit a 
wonderful parallelism and, to a large extent, may be synchronized. 
Approaching now the proper subject of this paper, I may observe 
that, although my opportunities for study in South America have 
been very limited, yet I have had occasion during the last two years 
to familiarize myself with a large part of the geological literature of 
that continent. While studying the descriptions of Darwin, Schom- 
burgk, Jannetaz, Liais, Hartt, Derby, Brown and others, I have been 
frequently impressed by the strong resemblance in composition and 
sequence which they revealed between the stratified crystalline form- 
ations of North and South America; and my present purpose is to 
indicate the correlations which these comparisons have suggested. 
Thus doing for the eastern half of South America, though of neces- 
sity much less satisfactorily, what Dr. Hunt and others have done for 
