Bubble lights were first manufactured by Noma, who bought the patent for them from their inventor, Carl Otis.
The bubbling is caused by a combination of a chemical and the heat from the lights. These lights were one of Noma's best selling products, and were also manufactured by Paramount, Peerless, USALight, Reliance, Renown, Alps and others.
Most bubble lights are variations of the familiar "candle" shape, but some figural bubble lamps were also produced. These figural bubble lights are rarely seen today.
A great resource we found for identifying old bubble lights is this bubble light identification page.