No. 12. Indurated clay; its colour is bluish gray, structure slatose; fracture approaching uneven; hardness inconsiderable. Impressions of small leaves occur in this, but are not numerous; they apparently consist of one species alone.
No. 13. Compact argillaceous sandstone; composed of quartz, felspar, and their laminæ of talc, united by an argillaceous cement; its colour is brownish gray. Nodules of clay ironstone occur in considerable abundance in this rock; they are formed by concentric layers, around a nucleus, which is the same in composition as the mass of their bed. Their size varies from that of a nut to an apple.
From Mr. Jessup's MS. Report.—James.
[PART II][98]
Containing the Calculations of Observations made by Major Long and Lieutenant Swift, on a tour from the Council Bluffs on the Missouri river, westward along the river Platte to its head waters in the Rocky Mountains,—thence southwardly to the head waters of the Arkansa and Canadian rivers,—and down said rivers to Belle Point, performed in 1820, under the command of Major S. H. Long, of the United States' Topographical Engineers.
Note.—The instruments used in making the following astronomical observations, were a portable sextant of 5 inches radius, graduated by the assistance of the vernier to 30˝, made by Cary, London, accompanied by a mercurial artificial horizon with a glass frame, and an excellent patent-lever watch, by Robert Roskell.
| June 20, 1820. | Meridian altitude of sun's lower limb | 72° 23´ |
| Extent of horizon, (a level sheet of water) | 700 yards. | |
| Height of observer's eye above horizon | 3½ feet. | |
| Index error—4´ 15˝. Latitude deduced | 40° 59´ 15˝ N. |