i86 The American Geologist. September. i904 
The Otero Formation, as already described, consists 
of marls with gypsum and saline beds. The upper surface 
wherever exposed seems a plane and the line between the 
Otero and Tularosa beds is sharply defined. Wherever the 
level of the Otero beds is reached, as in the playas and 
streams about the margin of the basin, saline conditions pre- 
•vail. Sometimes these salt flats are bare and covered with a 
thick deposit of salt and alkalis as well as gypsum, while in 
other cases there may be some soil commingled and the sur- 
face is sparsely covered with "salt bush," "salt grass" and 
other plants of the distinctly saline flora. Along the margins, 
where the fans from the canons have added to the original 
deposits, the flora is increased by greise-wood (Laria) mes- 
quite and the typical desert facies. The salts upon the playas 
differ in different cases. In some ca^-es, when dry, there is 
a layer of nearly pure salt (chloride of sodium) several 
inches thick. More frequently other salts occur in considera- 
ble abundance. When carbonate of soda preponderates it will 
often form a dense crust' in which little common salt is a 
prominent ingredient. Borax and carbonate of potassium also 
occur under somewhat different conditions. There seems 
to be considerable uniformity in the amount of salt in the 
several divisions. Thus in the series of playas north of the 
barrier above described as separating the great western salt 
lakes into two portions an average of two samples gave over 6 
per cent of salt, while to the south of the Soda lake which is 
the southern part of this chain gave an averge of 14.6 per 
cent, besides large quantities of other =alts. This might seem 
to indicate a tendency to concentrate toward the southern 
part of the area. Nevertheless the area near "Mai Pais 
spring" which issues from the southern end of the lava 
sheet, and the flats of the northern end of the old lake Otero 
are heavily charged with salt. An average of over 15 2^^ 
cent was found here without including several lakes whence 
commercial supplies of salt have been taken and which afford 
a continuing supply of the pure mineral. 
All the arroyos in the east side of the basin are saline. 
The water flowing in Lost river, for example carries 7 per 
cent salt while soil in Tularosa arroyo runs 7.8 per cent. The 
salt lake into which Lost river flows is saturated brine and 
