Occasionally one comes across a carbon filament lamp that has a porcelain Thomson-Houston base. The following is taken verbatim from Electrical World, Vol XXIX, No 12, Mar 20, 1897, pg 397; the lamp image has not been included:

"The increasing use of 220-volt distribution systems for incandescent lighting has presented some problems in lamp base insulation which are by no means easy of solution. The ordinary brass base cemented to the lamp with plaster of Paris has proved very undesirable for this purpose in street railway cars, outdoor sign work and in mills and cellars where there is much dampness or corrosive fumes.

"To meet the demand for a lamp base which would obviate as far as possible these difficulties, the Bryant Electric Company, Bridgeport, Conn., has placed upon the market the porcelain base here illustrated. The finest grade of glazed porcelain is used, the contact rings being cemented in such a way that their union with the porcelain is very rigid. The peculiar advantages that this highly insulating substance possesses for this purpose are obvious. The readiness with which it can be cleaned is no small addition to its other valuable qualities. The bases have not been placed upon the market for general sale, but are made only for lamp manufacturers."