Georgian (18th Century)
Georgian windows were designed with a special Classical relationship between their widths and heights, known as the Golden Mean (approx 1:1.6). The glass panes were designed to conform to these same proportions. The overall effect was a carefully contrived harmony between glass and window frame proportions. Even where opes had to depart from that proportion, the glass proportions were maintained in that ratio, by having a different number of panes in the top and bottom sash, as illustrated below.
See Also
How to Identify a Georgian House