NATURAL RESOURCES LITTLE. 225 
inadequate. A better cloth was thereupon developed in this country 
from long staple mercerized cotton, and over 10,000,000 yards were 
woven and delivered. 
At the time of the armistice the United States had contracted for 
more than 100,000 aircraft engines, of which over 64,000 were Liberty 
engines, for which Ford was turning out 2,000 rough cylinders a day. 
At one time the entire airplane program was jeopardized by the 
limitations of the supply of acetate of lime, the source not only of 
acetic anhydride essential to the production of the cellulose acetate 
used for airplane dopes, but also of acetone required by the British as 
a solvent in the manufacture of cordite. In this situation Arthur D. 
Little, Inc., had the satisfaction of developing in its laboratories 
two alternative dopes which made no demand upon the acetate of 
lime supply. One had for its base cellulose butyrate, the acid for 
which was derived from Pacific Coast kelps. The other used a solu- 
tion of zein, a protein existing in the germ of Indian corn. In all 
more than 1,300,000 gallons of airplane dopes were made in the 
United States. 
At the date of the armistice we had produced 11,754 planes and 
were making over 10,000,000 rounds of aircraft ammunition per 
month. 
Besides the high explosive bombs used in aero warfare, interest 
attaches to other types, among which may be mentioned the incen- 
diary bombs and the dummy bombs for target practice. The former 
Aveighed 40 pounds each and were loaded with an oil-emulsion- 
thermit mixture and metallic sodium, the latter to nullify efforts 
to put out the fire by the use of water. Over 122,000 incendiary 
bombs were ordered, and 86,000 were received. The demand for 
dummy bombs was even greater. These were made of terra cotta 
at a cost of about $1 each. They carried a small charge of phos- 
phorus and a loaded paper shot-gun shell. On contact they emitted 
a puff of smoke to advise the aviator of the accuracy of his aim. 
Before leaving aviation supplies mention may well be made of the 
alloy resistance wire woven into the aviator's clothing to supply 
warmth on the passage of an electric current. 
The war vastly extended and developed the old art of camouflage, 
and its practice made great demands upon burlap from India, which 
was used hj the British and ourselves, and upon raffia from Mada- 
gascar, which the French employed. Both materials were employed 
in strips, woven into fish net and wire netting, and colored with an 
oil emulsion paint. Some types of battery positions required 4,000 
square jurds of camouflage cover, and hangars and hospitals took 
great amounts. All told, we required for these purposes alone about 
3,000,000 square yards of burlap a month. 
