ASSOCIATION OF AMERICAN GEOLOGISTS. 
33 
feet 
B. Buff colored limestone . ^ . . . 20 
4. Soft saccliaroid sandstone . , . . , 40 
5. A portion covered by soil .... 40 
6. Brown magnesian limestone, resembling the cliff 
lithologically, but is nearly destitute of fossils . .190 
Tbis last is exposed only at low water , , , 495 
III. A section from Blue mounds to Wiskonsin River, exhibit- 
ing the following descending series of rocks : 
1. Beds of siliceous chert, containing the fossils of the 
cliff, and forming the peaks of the mounds . . .410 
2. The cliff limestone, containing lead ore in its lowest 
portion 169 
3. The blue fossiliferous limestone, very thin, some« 
times wanting 0 
4. Saccharoid sandstone ..... 40 
5. Alternations of saccharoid sandstone and brown 
magnesian limestone . . . . . ,188 
6. Sandstone ....... 3 
7. Lower magnesian ...... 190 
1000 
By lower magnesian limestone is not meant the magnesian 
limestone of Europe. The name was given by Dr. Owen, in 
contradistinction to the cliff limestone, (which is the upper 
magnesian,) both containing magnesia. The cliff limestone is 
properly divided in three portions, viz. : 
Upper Beds — more regularly stratified, and less frequently ver- 
tically fissured than the middle or lower; also more rich in 
siliceous fossils, containing layers of chert, and indeed passing 
wholly into masses of flinty rocks, containing also good iron ore, 
and much crystallized carbonate of lime ; but lead more rarely 
and in unprofitable quantities. The fossils most frequently 
VOL, II. NO. XIV. 1? 
