184 The American Geologist. September, 1904 
of gypsum might render soils to some extent immune to 
droughts. 
The dazzling whiteness of the sand is strongly contrasted 
to the unusual greenness of the vegetation. Travel over the 
sands in the day time during summer is dangerous and the 
peril is even greater during severe wind storms in winter. 
Two travelers perished on the day following the escape of our 
party on a previous visit in January. Seven hours rapid walk- 
ing over the sands and adjacent salt fiats without food or 
water in July convinced one of our party of the grave pos- 
sibilities of any miscalculation of time or distance in this 
region. These natural difficulties are greatly increased by the 
undrinkable nature of the water of springs and wells in this 
region. Animals and even men become innured to its use 
but vast numbers of domestic animals perish from its effects. 
We lost a valuable horse from the effects of drinking from 
a well used by hundreds of animals and the occurrence is not 
unusual. All watering places are surrounded by carcasses of 
cattle and horses. 
To the residual lakes found in the old basin the de- 
scription of Russell applies, and as some interest attached to 
the parallel, we again quote:* "Other lakes, which indicate 
still more pointedly the contrast between an arid and a 
humid climate, we may call playaf lakes. These are broad 
sheets of shallow water, covering many square miles in 
winter season, but evaporating to dryness during the summer, 
their beds becoming hard, smooth mud plains or playas. In 
many instances a lake is formed over a playa during a single 
stormy night, only to disappear beneath the next noon-day 
sun." 
The effects of the universal whiteness on life is seen in 
the case of certain lizards, beetles and spiders, which become 
nearly perfectly white. A question of considerable biological 
interest arises in this connection, namely, whether a long in- 
terval of time was necessary for such adaptive changes, or 
whether the adaptation occurs as a result of direct and 
prompt nervous reaction such as the paralysis of the nervous 
• L. c. p. 198. 
+ The word playa primarily means a shore or beach. It would be inter- 
esting to know how it comes to be applied to these mud flats. One is tempted 
to think of a confusion of terms. C. L. H. 
