1881 to 1882

This base, which came out in late 1881 or early 1882, is similar to that of earlier bulbs except that the cone-shaped copper ring which served as a second contact terminal is eliminated.  This base had a copper screw shell with two or three threads (which served as one terminal) molded over a plaster of paris insulator.  But the bottom of the plaster base now had straight-sided copper contact for the second contact terminal (eliminating the separate cone-shaped copper ring).  The base was cemented to the neck of the bulb by a thick ring of plaster of paris between the bulb and base.  The small plaster of paris collar above the base for holding and screwing the bulb into a socket was still retained.  The wooden socket itself would have female threads to place and tighten the base in.  It is interesting to note that the base of this bulb will even fit into today’s sockets.

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