77 
the list of the known desert mollusks, 
two of them distributed over the whole 
United States and perhaps a third also. 
A curious thing was noticed where the 
clay from the gold washings had settled 
in the holes, not forming level layers on 
the bottom only, but instead settling on 
the sides as well, and forming thick and 
unequal layers. These remarkable for- 
mations of strata were often exposed by 
_other washings, showing the irregularly 
curved and distinctly marked stratas of 
clay (with other dirt), unequal in thick- 
ness. The holes may have been made 
by horses after the deposit, the layers 
pending under the weight, as they were 
unbroken. C. R. Orcurt. 
—_—_—_—_+-@+—___—_ 
WATER ON THE COLORADO 
DESERT. 
HE Colorado river is one of the main 
sources of water on the Colorado 
Desert; the numerous sloughs, 
lagoons and so-called wells, including 
New river channel, Lake Maquata and 
the Dry lake, are all dependent upon itS 
annual overflow ,—and when the summer 
freshet subsides without the Colorado 
river having filled its own banks, as is 
very frequently the case, all these places 
are dry. In fact, of iate years an over- 
flow is rather an exception than the rule. 
In 1884 there was a great overflow which 
filled everything to overflowing on the 
desert, but from that year until the sum- 
mer of 1890 no overflow of note has been 
recorded. It will therefore be recognized 
asa truism that New riverand its lagoons 
cannot be relied upon as an unfailing 
source of water, and the series of wells 
that once existed along the old emigrant 
frail are uo longer very useful to the 
occasional traveler, and never were re- 
lied upon for any large supply of water. 
Sometimes rain on the desert will par- 
tially fill the numerous holes, lagoons 
and depressions, where it remains until 

evaporated by the sun—the hard clay of 
this region being nearly impervious to 
water. . 
A sample of water taken from the Col- 
orado viver the 18th of September, 1890, 
upon analysis by the California State 
Mining Bureau shows upon filtration 
a sediment in the ratio of 4.861 gra;nmes 
to the liter. The water used by the rail- 
road at Yuma, Arizona, is first pumped 
into one of three tanks, each of a capac- 
ity of 100,000 gallons, where the water 
is allowed to settle. The tanks are about 
seven and a half feet in depth and forty 
by fifty feet on top, somewhat smaller 
proportioned at the bottom. The result- 
ing sediment after the water has stood 
for a few days is very variable with the 
season. In April, 1889, it varied from 
eight to fifteen inches of mud; in May, 
June and July, five to seven inches only; 
in August, from nine inches on the 4th 
to twenty-two inches on the 13th (the 
water standing only three days for this 
result) to six inches on the 28th; in Oc- 
tober and November the minimum of 
three inches of sediment was recorded, 
while in December from nine to thirteen 
inches were deposited. In August was 
the season of the annual freshet when 
the river was highest and most rapid and 
the sediment was correspondingly great. 
At high water the extraneous matter held 
in solution may be considered to be ap- 
proximately ten per cent. 
The water of New river and its lagoons, 
like the source in the Colorado river, 
holds a very considerable quantity of 
fine clay in suspension, and after long 
standing in the sun becomes more or less 
charged with organic impurities. It ap- 
pears tolerably free from soluble salts, 
not perceptible to the taste, but upon 
evaporation it becomes brackish and 
shows the presence of salt by a slight 
incrustation on the shores of the lagoons. 
The old emigrant trail from Yuma to 
California, later known as the stage line, 

