The word window originates from the Old Norse for "wind eye." It began as a peep-hole through the roof, then as a "door for the eye." But it was the invention of glass that allowed light to come through and a view of the outside while protecting the inhabitants from the elements. Architects would eventually grace building façades with innumerable repeating windows, or skip walls altogether once glass was perfected to allow for vast expanses of glass, floor to ceiling, ground to sky.
["Pledge of Allegiance Building" in Boston]
An intriguing thing about window glass is its ability to reflect, sometimes mirroring back more than it reveals, like some cagey types who charm while disclosing nothing. Or it blends the internal and external in accidental alliance, a fleeting liaison of light and shadow.
And then there's the ability of glass to project light, to create the imaginary in the shadow of the real.