496 .' BPOCAL SECTIONS 
1. Soft, crumbling, white quartzose sandstone, in heavy beds, ‘ 20 
2. Ash-coloured, argillaceous schistose limestone, with thin marly seams, ‘ 5 
3. Highly fossiliferous shell limestone, of a gray Fisk -blue colour, : . 13 
Both at the Falls of St. Anthony and this place, the fossiliferous beds are sur- 
mounted by from eleven to twelve feet of drift material, consisting of sand, gravel, 
and small boulders, on which rests a bed containing Lymnea, Cyclas, Physa, and 
Planorbis, in great quantities. This I traced for the distance of nearly half a mile 
on the same level, below the falls. On the trail which leads to St. Paul’s, about 
half a mile from the falls, and elevated from forty to fifty feet above the last-men- 
tioned deposit, I observed a white marl, highly charged with Lymnea, Cyclas, Pla- 
norbis, Valvata tricarinata, and other genera of lacustrine and fluviatile shells, such 
as now live in the neighbouring lakes and streams.* At Fort Snelling, the sand- 
tone is one hundred and fourteen feet thick; it is here of a pure white colour, 
composed of loosely cemented grains of quartz. 
Above this, we have twenty-two feet of fossiliferous limestone, with numerous 
organic remains, similar to those at the Falls of St. Anthony. The fossils of the 
upper beds are mostly casts, but the moulds often show the structure of the original 
surface. Many of the fossils have a coating of sulphuret of iron, which gives them 
a bright metallic appearance. 
The best section of these rocks that we have observed in Minnesota is at a Bae 
half a mile below Fort Snelling. The section here is as follows: 
1. White sandstone, without fossils, in thick beds, 92 
2. Soft Vict abe marlite, of a blue colour, in which no bulla’ were joie 
red, 
3. ikoiaha ovsatann, duncan with en full of itis. The seach 
common are Orthis testudinaria, O. tricenaria, Leptena sericea, L. 
deltoidea, L. planumbona, L. aliernata, Terebratula modesta, A. 
capax, Calymene senaria, Phacops callicephalus, Ceraurus pleu- 
rexanthemus, Isotelus gigas. We have also found in this bed por- 
tions of an Orthoceras, which must have been from two to three 
feet in length. It has likewise yielded somewhat abundantly a neat 
little species of Cytherina, exhibiting a punctate surface, besides 
several species of Graptolites. These layers effervesce freely with 
acids, and contain nearly sixty-five per cent. of carbonate of lime; 
they will probably afford the best rock for burning into lime of any 
of the beds in the neighbourhood.+ Thickness, . 15 
* See Sect. No. 
+ The semen of this rock is as follows: 
Carbonate of lime, ‘ : i j ; : 64-85 
- “magnesia, . ; , . ‘ , 13-75 
Insoluble matter, . ‘ k s ‘ 12-40 
Alumina, oxide of iron, ind duns peitins, : : ‘ : 7°50 
Water, « : : 3 eae 
Loss, : ‘ F i ‘ : : : 0-25 
