426 The American Geologist. Jane, 1894 
that exisl in the naming and correlation of the older rocks of the Lake 
Superior region. II. The geologj of Kekequabic lake in northeastern 
Minnesota, with special reference to an augite soda-granite, by U. S. 
Grant. This gives a geological description of a limited area and a pe- 
trographical description of the eruptive rocks, the most important of 
which are an augite-soda-granite and a hornblende-porphyrite-. III. 
Catalogue of rock specimens collected in northeastern Minnesota in 1892, 
bj I". s. Grant. IV. Preliminary report of a reconnoissanee in north- 
western Minnesota in 1892, by J. E. Todd. Here are given notes of a 
summer's work on the glacial geology and topography of tlie northwest- 
ern part of tlie state. No exposures of rocks older than the drift were 
Seen except where the Archean outcrops on the south shore of the Lake 
of the Woods. V. Field observations of N. H. Winched in 1892. This 
contains: notes on the Mesabi iron range; manganese oxide at Monti- 
cello: Republic and [shpeming, Mich.: Potsdam, N. Y.; Morrison county. 
Minn.: some problems of the Mesabi iron ore:* and remarks on the so- 
called muscovadyte or muscovado rock. A number of pages is given to 
a review of the question of the first recognition of the unconformity 
between the two great iron-bearing formations (Upper and Lower Htt- 
ronian) in tlie lake Superior region, and especially in the Marquette dis- 
trict: the author thinks that he was the first to recognize this break and 
to appreciate its importance, and that Prof. R. I). Irving did not recog- 
nize it. In his notes on the Potsdam region Prof. Winched seems in- 
clined to put the true Potsdam sandstone where it is usually placed by 
geologists, at the base of the Upper Cambrian, and not at the base of 
the Lower Cambrian where he lias heretofore insisted that it belonged. 
He thus no longer regards the Sioux quartzite and the quartzite at the 
base of the Animikie as the western equivalents of the Potsdam of New 
York. VI. Additional rock samples collected in 1892, to illustrate the 
notes of N. II. Winched. VII. Additions to the library since the report 
lor L891. - G. 
Tht Trap Dikes of tin Lake Ohamplain Region. By .1. F. Kemp and 
V. F. Marstehs. U. S. Geol. Survey. Bulletin 107: (52 pages. 4 plates. 
1893. In the vicinity of lake Champlain. and especially abundant along 
the shores of the middle part of the lake, are numerous dikes of light 
colored acid rocks, feldspathic porphyries or trachytes (bostonites), and 
darker basic ones. The latter include diabases, camptonites, monchi- 
quites and fourchites. The diabase dikes are very numerous in the 
older rocks on the west side of the lake and frequently cut the iron ore 
bodies: they pass into camptonites. which are also quite common. The 
monchiquite and fourchite dikes are not so plentiful, of the latter 
only one being known. A petrographical description of each of these 
rock types is given and there are some remarks on the classification of 
dike rocks, the following divisions of the more basic dike rocks being 
made: A. Syenitic lamprophyres, including (1) minettes and (2) voge- 
sites; 1>. Dioritic lamprophyres. including (1) kersantites, CD campton- 
*Already published in the American Geologist, vol, x, pp. 169-179, Sept., lsy^. 
