704 C.K LEIGH, 
The structural relations of the three belts of Cambrian blue lime- 
stone with the gneiss and white limestone are such as to indicate uncon- 
formity. Along the normal contacts of the blue and white limestone 
the quartzite intervenes between the two. The bedding of the blue 
limestone and underlying quartzite is everywhere conformable, while 
the dip of the foliation of the white limestone and the gneisses is dis- 
cordant with this bedding. 
Isolated patches of Cambrian quartzite are found within the white 
limestone area. In one place a crevice in the white limestone is filled 
with the Cambrian quartzite containing undoubted pebbles of the 
white limestone. 
Comment.—The results above presented bear evidence of close and 
careful field study. The pre-Cambrian age of the white limestone is 
clearly proven, thus satisfactorily disposing of a much disputed question. 
There now remains the question of the origin of the gneisses. In 
this connection attention may again be called to the marked similarity 
of the limestones and associated. gneisses of the New Jersey area, to the 
pre-Cambrian limestones and associated gneisses of the Adirondack and 
Original Laurentian districts to the north. In a general way it would 
seem that the story worked out for one of the districts may perhaps 
apply to the others. 
Weidman* describes the pre-Cambrian igneous rocks of the Utley, 
Berlin, and Waushara areas, in the Fox River Valley of Wisconsin. They 
range from volcanic flows to masses of deep-seated origin, with corre- 
sponding textures. The rock of the Utley area is a metarhyolite, at 
Berlin a rhyolite-gneiss, and in the Waushara area a granite. Analyses 
of the rocks of the three areas show a close similarity in chemical 
composition, and it is believed that the rocks represent phases of a 
single parent magma. ‘The rocks have been metamorphosed to differ- 
ent degrees, and the results of the metamorphism, particularly of the 
feldspars, are described in detail. 
The crystalline rocks are unconformably overlain by flat-lying Pots- 
dam and Ordovician sediments. From their similarity in composition 
to the Baraboo volcanics, which are considered to be of Keweenawan 
age, it is believed that they belong to the same province, and are there- 
fore of Keweenawan age. 
*A contribution to the geology of the pre-Cambrian rocks of the Fox River Val- 
ley, Wis., by SAMUEL WEIDMAN: Bull. Wis. Geol. & Nat. Hist. Surv., No. III, 1898, 
pp: 63. 
