10 The Delta of the Rio Colorado. 
a saline plain a few miles in extent innumerable small mud cones, sol- 
fataras, and boiling pools of mud and water emit steam, smoke, and 
sulphurous gases, accompanied by a dull rumbling sound. According 
to the traditions of the Cucopa Indians, formerly a member of the 
tribe accused of sorcery or other serious crime was sent back to his 
evil master by the simple process of dropping him into a pool of boil- 
ing mud—an obvious entrance to his abode below. Flood-water 
covers a number of the small volcanoes, and then quite an extended 
area of the lake is agitated by the eruptions from below. 
The largest of the volcanoes, known as the “Cerro Prieto,” stands 
on the margin of the gravel slopes leading down from the main range 
of the Cucopa Mountains and rises as an irregular black mountain 
to a height of 750 feet, with several minor craters on its sides. The 
main crater is regular in form, and shows indications of activity at no 
remote time, although the bottom of the bowl now bears the charac- 
teristic vegetation of the desert, but including some species not now 
known elsewhere. In connection with the volcanoes are some boiling 
springs, which come to the surface a few feet above the level of the 
flood-water which flows from Volcano Lake into the Hardy. Im- 
mersed in the steaming water is a blue-green alga, which has been 
hitherto reported only from similar hot springs in Algeria, offering 
a problem in distribution the solution of which cannot even be con- 
jectured. 
The portion of the delta included in the Salton basin, which lies 
below sea level, and which is mostly within the State of California, is 
a true desert by means of its aridity and the saline character of the 
soil; consequently the plants and animals are referable to the Colo- 
rado desert, of which it in reality forms a part. The area actually 
irrigated by the river in normal low water and flood, however, is sur- 
rounded on all sides by desert and salt water, and is in reality a biolo- 
gical island. As such it offers an interesting comparison with the 
Cucopa Mountains, which limit it on the southwest, and which also 
constitute a sharply-defined life-area. 
The quantity of food furnished by the swampy jungles is sufficient 
to support a vast amount of native animal life, and furnishes inviting 
feeding grounds for migrating birds. The countless millions of 
young willow and poplar shoots supply food for the beaver, which — 
bids well to hold out long in the impassable bayous and swamps 
against its trapper foe. 
The soil, climate, moisture, and temperature of the entire delta are 
fairly uniform, and also differ but little in elevation and exposure—a 
condition which tends to promote the multiplication of the number of 
Se ponapte eR 
