By the early 1800's, most large American cities had public gaslight until electric lighting took its place in the later part of the century. Early electricity, however, was undependable and lighting fixtures that could use both gas and electric became popular, although short-lived.
In general, shades which face downwards were made for electric light bulbs and have smaller 21/4" fitters. They are often referred to as tulip shades. 21/4"
tulip shades are the most versatile of all glass shades. They originally debuted in the earliest of electric lighting fixtures to reduce the glare but are still used today on sconces, desk lamps, pan lamps and other hanging lamps. Although there are exceptions, this is a good rule of thumb to go by.
Mission style /
Art Deco style
Petal Flower /
Aurene Art Glass
Gas and Electric Combinations