242 The American Geologist. October, 1904 
demonstrate, by the strength of the same theory, why Mars 
has two moons. 
There are many other things that could be brought against 
the nebular theory, for instance, the question about the origin 
of the comets, which it cannot answer; but since we have al- 
ready shown its untenableness, we cannot gain anything by 
further argumentation against it. We may add, however, that 
what we have said so far, will appear much clearer and be more 
easily understood as we go on with the explanation of the real 
causes which have produced the natural phenomena, which, as 
we have shown, hitherto have been so totally misunderstood. 
(To be Contimied.) 
THE BARABOO IRON ORE, 
By N. H. Winch ELL, Minneapolis. 
One of the notable publications relating to the iron ores of 
the Northwest is that of Dr. Weidman, of the Wisconsin 
survey, lately issued by the State of Wisconsin.* According to 
the report this iron ore occurs in the "pre-Cambrian,'' in 
which are included rhyolyte, granite and dior>i;e, occurring 
in isolated outcrops, these all being considered parts of the 
Archean. The rhyolyte is a very hard, pinkish red rock which 
is usually unweathered and breaks under a stroke of the ham- 
mer with sharp conchoidal fractures. It contains niunerous 
crystals of pinkish feldspar and translucent quartz, which are 
imbedded in a very fine matrix or ground mass. It fractures 
sometimes naturally in all directions, so that it appears about 
the outcrops in the form of multitudes of small angular pieces. 
It is frequently veined by quartz. It is described by Dr. Weid- 
man as having been a surface or volcanic igneous rock, its 
groundmass representing the glassy part of the igneous flow, 
cooled too quickly to become entirely crystallized. It is dis- 
covered microscopically that the crystals of quartz and of 
feldspar contained in this rhyolyte have sometimes been bro- 
ken, and that between the parts thus formed the viscous 
magma has flowed. In other cases tliese crystals are bent. 
These distortions are assigned to a date prior to the solidifica- 
* "The Baraboo Iron Bearing District of Wisconsin," Samubl Weipman. 
Wisconsin Geological and Natural History Surrey, Bulletin -No. 13, Madison, 
1904.. 
