The Summary of Physics Restored

77Air in its entirety is heaven, the field of the universe, nature's sieve, through which the powers and influences of other bodies are transmitted. It is an intermediate nature joining all the scattered natures of the universe; the subtlest smoke, kindled by celestial fire into light like an immortal flame; the subject of light and shadow, day and night. It cannot tolerate a vacuum. Foremost among transparent things, it most readily receives almost every quality and affection, yet retains none with great tenacity. It is close to spiritual nature and is therefore designated by the name spirit when the philosophers' secrets are discussed.