One of the most reliable ways to prevent windows from frosting is to cut a space through the window frame at the bottom and another at the top of the windows that front on the street. Then close up the back of the window from the store proper. In this way you keep a currant of cold air circulating inside of the show window, making the interior of your display window the same temperature as the street all the time. The cold air constantly passes in and out, keeping the glass just as cold inside as it is on the outside. Another method frequently adopted is to run a tin or other metal tube about one inch in diameter set along the bottom of the pane. This is pierced with holes along the top and one end is extended downward and shaped like an inverted funnel. Under this a lamp or gas jet is kept burning, the heat from which passes along the tube and out of the perforations up against the window and prevents the formation of frosts. . It is also stated this difficulty can be entirely obviated by rubbing both sides of the window two or three times a week with a cloth dipped in glycerine.