RELATIONS OF TRENDS OF COAST LINE AND STRATA. 265 
Duluth and Temperance River, the coast line has crossed some 17,000 feet 
of strata. 
Two miles below Temperance River, in Sec. 28, T. 59, Rents W.,..& 
descent of the coast line in geological horizon begins to be perceptible. 
This descent continues without interruption for a distance of 70 miles, or to 
the end of the Minnesota coast, at Pigeon Point. From Temperance River 
to Grand Portage both coast line and strata curve more and more to the 
eastward, but the strata change direction more rapidly than the coast line, 
so that they cut it at a small angle all the way, producing points like those 
described as characterizing the coast line west of Temperance River, but 
with the difference that the points now project eastward, instead of to the 
southwest At Grand Portage, the Keweenawan beds striking out under 
the lake, the Huronian or Animikie slates appear from beneath. 
The Minnesota coast line, looked at as a whole, presents a sort of flat 
crescentic shape, with the concavity towards the lake. The same is true of 
the courses of the strata, but the crescents formed by them have a much 
smaller radius, and hence intersect that formed by the coast line, trending 
more to the north at the Duluth end, and more to the east at the Grand 
Portage end. In following the coast, then, from the slates of the Saint Louis 
River to Grand Portage, we ascend in geological horizon to a point near Two 
Islands River, and from a point just east of Temperance River descend again 
to the same slates at Grand Portage. Since the exposures are almost con- 
tinuous, the coast line thus gives a complete cross-section of the whole 
thickness of Keweenawan beds present in northeastern Minnesota. Since 
the junction line between these Keweenawan strata and the underlying 
slates makes quite a large angle with the lake shore at both ends, and since 
the prevailing dips are so flat, it follows that the first-named rocks spread 
far back into the country. At the mouth of the Brulé River they lie some 
12 miles back; at Grand Marais 18 to 20; at the middle of the crescent, 
near Manitou River, 30 miles, at about which distance they remain until 
near Duluth and the Saint Louis River. The slates themselves have about 
the same flat position, so that they, in their turn, spread over a wide belt of 
country. 
Equally simple with the general structure as thus laid down, is the 
