INFLUENCE OF THE DESERT ON LIFE. ae e 
that has been suitably placed in a hole in the ground below. A cut is 
made above the bucket to allow the liquid to exude, while the process is 
hastened somewhat by building a fire under the ends. 
The experiences of the expeditions from the Desert Laboratory made 
it evident that a still or condenser by which even a small quantity of 
drinkable water could be obtained from the abundant sap of these plants 
or from alkaline waters would greatly facilitate field-work. After some 
experimentation the form adopted was one designed by Mr. Godfrey 
Sykes, in which the cactus pulp or liquid to be distilled was placed in a 
boiler of pressed steel. This boiler has a capacity of about 2 gallons and 
is built up of two pressed-steel kettles, one of which is inverted over the 
other and fastened by a riveted seam. An opening 4 inches in diameter 
in the bottom of the inverted vessel received a threaded fitting to which 
is attached a half-inch pipe with an elbow. Sections of pipe 30 inches 
long with conical friction joints are carried, and as many are fitted as may 
be necessary to secure condensation. This apparatus may be set up 
anywhere, and the cooling of the steam escaping through the condensing 
pipe may be effected in the air, by embedding in the earth, or by a drip 
from cloths. A capacity of several gallons per day has been shown by 
this apparatus, an amount that would enable a party to make a stay 
at a locality in which the untreated water would be wholly undrinkable. 
This apparatus has the additional advantage that the replacement of 
the outlet of the boiler with a screw plug makes it a suitable Ee for 
carrying a supply on the march. 
Some experimentation has been made for the purpose of designing 
a solar condenser in which the vapor coming from a water surface under 
the influence of the sun’s rays would be condensed on a cooler shaded 
portion of the glass top, and the collected drops conducted to a receiver. 
Devices of this sort constructed of non-soluble glass are used at the 
Desert Laboratory to secure water of a high grade of purity for use in 
injection experiments with plants. These work very slowly, however, 
and no form of this apparatus has yet been designed that would be of 
any practical value in life on the desert. 
