From Mosley's pamphlet, "The Hugo Ballin Murals at the Griffith Observatory" (Los Angeles: Published by the Griffith Observatory, Department of Parks and Recreation, City of Los Angeles, 1998):

“Men first looked to birds (extreme left) for guidance. Archytas is said to have made a wooden pigeon that could fly in 400 B.C. Behind Archytas stands Roger Bacon (1214-1292), the English philosopher whose floating metal ball demonstrated the principle of displacement. 

Seated in the foreground is Francesco de Lana (1631-1687), who holds a model of his proposed flying boat to be lofted by four large copper balls from which the air had been evacuated. He prophesied coming air wars: ‘No city can be secure against such an attack (by air). Ships may be at any time placed directly over it, and descending, may discharge soldiers.’

In the rear center stands Leonardo da Vinci (1452-1519), the great Italian painter, sculptor, architect, engineer, musician, and natural philosopher. He studied the flight of birds and established fundamental principles of aviation. In his concept of a flying machine, oars would be operated by a system of pulleys. Muscle power was inadequate, but if he had had a gasoline engine, he would have successfully navigated the air.

The first successful glider was made in 1678 by Besnier, a Frenchman, who placed two adjustable cloth kites over his shoulders and soared over a house.

At upper right is a Montgolfier balloon, which in 1783 made the first lighter-than-air flight. The balloon was filled with air and heated over a fire. Hydrogen and helium balloons came later.

At bottom we see a ‘modern’ propeller-driven airplane and a gyroscope.”

In this panel, Ballin avoids allegorical figures entirely and instead features historical figures from a variety of periods who contributed to the development of modern aviation. Noticeably absent from the panel were the innovators of a more recent period: the Wright Brothers, who in 1903 became the first aviators to build an aircraft that could support a human passenger in flight. Instead, Ballin represents the advancements of aviation in his own lifetime with the technologies themselves, rather than the individuals who developed them. These "modern" technologies - a Montgolfier balloon, propellor plane and gyroscope - are positioned in the right side of the panel, giving it a chronological arc as the viewer's eye moves left to right. The sky in that portion of the panel looks realistic and colorful while the sky behind the ancient scientists seems cloudy, and the "modern" propeller plane seems to be breaking through the clouds, suggesting that Ballin wanted to emphasize the contrast between the past and his "modern" times.

To differentiate between each of the historical figures included in the panel, Ballin uses props and costumes to signal their identities: each man holds a physical embodiment of his theoretical concepts and wears a robe from his historical period. Even though chronologically Besnier is the most contemporary of the scientists depicted, he wears the simplest of outfits, giving the impression that his experimental glider was of a more ancient, primitive age, perhaps in an attempt to increase the contrast with the "modern" propellor plane behind him and differentiate these historical men from the "modern" aeronautics engineers of the 1930s.

Caption excerpted from John Mosley's pamphlet, "The Hugo Ballin Murals at the Griffith Observatory" (Los Angeles: Published by the Griffith Observatory, Department of Parks and Recreation, City of Los Angeles, 1998).