1 30 The American Geologist. August, 1899 
than the anorthosyte. The author regards it as also younger than the 
noryte and monzonyte, arguing that, as it departs much more widely 
in composition from his calculated parent magma, time for such dif- 
ferentiation is necessary. The same reasoning is applied to the Lister 
adamellyte, which i? younger than, but only in contact with, the anor- 
thosyte. The adjoining banatyte is younger than the Lister adamel- 
lyte since it sends a dike into it. 
An interesting comparison of these and the Christiania eruptives 
follows, accompanied by numerous analyses. It is interesting to note 
that in this country the Adirondack and eastern Massachusetts igneous 
rocks present a very similar contrast which is not likely to be simply 
fortuitous. 
The Ekersund order of eruption is anorthosyte, followed by slightly 
more basic norytes and monzonytes, then by the acid adamellytes and 
granites, finally by the somewhat more basic banatytes, with later basic 
diabases. The Christiania order is basic through intermediate to acid, 
followed by basic diabases. This difference is explained by arguing 
for the differentiation of the Christiania magma before eruption took 
place, while the Ekersund anorthosyte appeared before differentiation 
of its magma, after which differentiation of the remainder occurred, 
then further eruption giving first noryte and adamellyte from the basic 
upper part followed by the acid material from the center. To account 
for the appearance of the more basic banatyte further differentiation 
before eruption is suggested. 
The age is supposed to be later Silurian or post-Silurian since the 
Bergen anorthosyte cuts Upper Silurian rocks and they are assumed 
to be of about the same age. In the district under consideration the 
only certainty arrived at is that the intrusives cut pre-Cambrian 
gneisses. h. p. c. 
MONTHLY AUTHORS' CATALOGUE 
OF American Geological Literature, 
Arranged Alphabetically.* 
Bain, H. F. 
Geology of Carroll county. (Geol. Sur. Iowa, vol. 9, pp. 49-107, 
pi. 2, map, 1890.) 
Bain, H. F. 
Report of the Assistant State Geologist [Iowa]. (Iowa. Geol. Sur., 
vol. 9, pp. 25-27, 1899.) 
*Tliis list includes titles of articles received up to the 20th of the preceding 
month, including general geology, physiography, paleontology, petrology and 
mineralogy. 
