94 
beginning with the loose-grained sandstone, is evidently one, 
and is called Eocene. No fossil of marine origin is found 
here, which can in any way assist in determining the age, for 
the rock is of such a character as not to preserve shells. But 
followed northward, the sandstone at some points shows 
calcareous bands containing occasional mollusks; and when 
we reach St. Vrain’s Creek, nearly fifty miles north from Den- 
ver, where the general section is the same as at Cafion City, 
these bands are very numerous and rich in fossils. Some of 
the beds contain Halymenites major, in such profusion as to 
be fairly matted with it; while interstratified with these are 
other layers containing Ammonites lobatus, Mactra alta, 
Anchura, Nucula cancellata, and many other species very 
characteristic of the Upper Cretaceous. These fossils overlie 
the lignite beds of Platteville. As to Halymenites major, it 
needs only to be said that in New Mexico, all the geologists 
have used it as a very characteristic fossil of the Upper 
Cretaceous. In this connection it may be said that the 
Cretaceous is pre-eminently a lignite-bearing group. In New 
Mexico and Western Colorado, as well as in Southern 
Utah, enormous beds of lignite occur in the Lower Cretaceous, 
and even in the lower portion of the Middle Cretaceous. 
There seems to be no indication of the Kocene age of the 
lignites of Hastern Colorado, save a few fragmentary leaves ; 
while all other evidence shows strongly that they are of the 
Upper Cretaceous. 
Mr. Henry Newron read a paper on American Iron Ores 
suitable for the Manufacture of Steel.* 
After describing the great changes which the introduction 
of the Bessemer process has led to, involving almost a new 
era in the metallurgy of iron, and calling for a purity and 
uniformity in the pig-metal employed, and a scientific skill 
and exactness in the process of its production, that were be- 
fore unnecessary and unknown, Mr. Newton proceeded to 
give the best results attained touching the maximum amounts 
of the three chief contaminating ingredients, phosphorus, 
sulphur, and silicon, in ores that are used for the production 
of Bessemer steel. The silicon should not exceed 2.5, the 
sulphur .05, nor the phosphorus .10, as average maxima. 
Passing then to the main question of the paper, whether 
the United States can furnish, out of its vast and numerous 
* This paper will probably appear in the Annals, Vol. XI, No. 3. 
