Spherical ballooning, some of the requirements (1917)
McCullough, Paul James, 1881- · Saint Louis, The Mangan printing company · leaf 31
SOME OF THE REQUIREMENTS 25 the aeroplane had suddenly increased its speed to 1 00 miles per hour, a condition demanding wide margin of safety in strength of material and work- manship employed in its construction.
Balloons
Internet Archive · Smithsonian Libraries · Public domain (published before 1931). Free to use for anything.
