404 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
the beds is parallel with the northeastern margin, and the dip is 20° 
to 45° toward the northeast. The beds maintain this attitude on both 
sides of the range, and they do not dip under the valleys on either 
side, as they have been supposed to do. 
Interbedded with the rocks of this series is a bed of colemanite 
(borate of lime), which, though probably not continuous, shows in 
outcrop in a number of places across the mountain, a distance of at 
least 25 miles. This constitutes the largest deposit known in this 
country and presumably the largest in the world. The bed has been 
opened low in the foothills on the east side of the mountain 4 or 5 
miles south of the Ash Meadows road. At this point the bed is 
visible for several hundred yards, and in the prospect pits it has a 
thickness of from 4 to 10 feet. It is said to exceed these figures, but 
no thicker sections were seen. The bed is composed of a mass of 
crystalline colemanite which mines readity and with little waste. 
In the western foothills of Funeral Mountain a bed of this mineral 
is exposed in the ravines for a distance of a quarter of a mile, and 
along this outcrop it varies in thickness from a few inches to 20 feet. 
At no point is it a solid, regular bed, but it consists of irregular masses 
and stringers of colemanite embedded in clay. The crystals are small, 
seldom exceeding a quarter of an inch in diameter, and the large 
masses are nearly pure. According to Superintendent Roach, of the 
Pacific Coast Borax Company, the largest mineral deposit occurs 
about 9 miles up Furnace Creek, on a nearly direct line between the 
outcrops just described At this point he reports a bed of boracite 
60 feet in thickness. Phis was not seen by the writer, but there are 
strong indications of the presence of minerals of this character, and 
it is probable that large deposits occur in this locality. 
Borax was once manufactured 2 or 3 miles north of the point where 
Furnace Creek emerges from the hills into Death Valley. The plant 
was situated on the margin of the alkaline marsh, and the crude 
material was derived from a certain part of the marsh where coleman- 
ite accumulated. It is now known that the mineral is derived by 
solution from the bedded deposit described above, and that its accu- 
mulation on a certain part of the marsh is due to the solution being 
carried to that place by a small stream. 
Death Valley contains an immense salt field, which may in time 
become valuable. It extends south from above the old borax works 
at least 30 miles. At the place where it is crossed by the road from 
Furnace Creek to Bennett Wells it is nearly 3 miles wide, and it prob- 
ably varies from 2 to 4 miles in different parts of the basin. The salt 
is not white, like the marsh at Salton, in Colorado Desert, but it is 
brown with dust and sand that is constantly being blown upon it. 
The salt stands in pinnacles 2 to 3 feet in height, making a surface 
so rough that it is impassable for a horse until the projections are 
pounded down with a sledge. With the implements at hand the 
