GEOLOGY. 103 
red argillaceous limestone, and a sandstone containing mica, are the sedimentary rocks of the 
Wahsatch mountains in the region of Swambah creek. None of them contain fossils. 
A bed of pure crystallized gypsum in the valley of the Ungot-tah-bi-kin creek, deserves to 
be particularly mentioned. The crystals are imbedded in a red or green marl si such abun- 
dance as to form a whole mountain of this valuable mineral. The section of the bed, about a 
mile from our road, extends about forty feet above the level of the soil, and it has very likely a 
considerable depth. 
In many parts of the Wahsatch and Tuilla mountains, a silicious rock, mostly calcedony and 
agate, breaks through a gray-white or gray limestone, infiltrating the latter, and forming 
veins of sometimes considerable thickness. The cañon leading to Swambah creek, and the ridge 
of the Tuilla mountains east of Cedar creek, consist of this infiltrated limestone. 
On Swambah creek I found an extraordinarily large block of crystals, apparently calcareous 
spar. They were white, semi-transparent, of granular fracture, and consisted of— 
Carbonate of lime 93.66 
Carbonate of magnesia 4.12 
Carbonate of protoxyd of iron 2.02 
Water.. 0.20 
100 
To the simple minerals occasionally mentioned heretofore, the following may be added : 
Dolomite, found in the valley of Ungot-tah-bi-kin creek. 
Hyalite, in the trapp-porphyry of the valleys of Coochetopa creek and Grand river. 
Sulphuret of molybdena, in the Wahsatch mountains. 
Asphaltum, in different places in the Wahsatch and Tuilla mountains. 
Had the Indian difficulties during last winter made geological excursion in Utah Territory 
admissible, the extraordinarily deep snows of that winter would have made them quite useless, 
if not impossible. For the same reason, our winter excursion into the Wahsatch mountains 
and Green river country, resulted quite unproductively in geological facts, and I am not able 
to add anything new to the geology of that country, as it has been described in former reports, 
with the exception, however, of a phenomenon which the Great Salt lake offers, and which not 
only possesses a scientific interest, but may be made of great importance to the development of 
chemical arts in the valley of the **Saints."' 
In summer the evaporation of the water of the lake is so great, and the solution of salts 
becomes so concentrated, that a part of them is deposited on the bottom of the lake. In some 
places, I have been told, this sediment has been found to be two feet thick. It consists of 
variable quantities of sulphate of soda and chloride of sodium, the sulphate exceeding by far the 
chloride, at least in the specimens which came under my examination. In the manufacturing of 
soda, an immense capital is annually wasted in producing this sulphate, which is finally con- 
verted into carbonate of soda. It can be had here for the mere trouble of taking it out of the 
e. 
Another interesting mineral production of the localities around that remarkable lake is found 
in great quantity at Alum Point, and in other places in Utah Territory. It is the manganesian 
or feather alum, a mineral of great use in the so-called tawing process, and an excellent material 
for preserving the skins of birds and other animals. It has rather been considered hitherto as 
a rare mineral. 
The composition of this alum does not seem to be constant; at least not in relation to its pro- 
portions of water. I obtained from one specimen 37.25 per cent. sulphuric acid, and 39.45 per 
cent. of water; and from another 37.26 per cent. sulphurie acid, and only 32.85 per cent. of 
water. There was no time to complete the analysis. 
In the regions between the Tuilla mountains and the Sierra Nevada, the desert character is 
