Two holes are bored through the base to correspond with the holes D and A in the bottom plate.  The glass tube is cut to make two pieces, each 4-1/2 in. long.  This can be done easily by filing a nick in the tube at the proper point and breaking it.  These tubes are forced into the holes bored in the base, and, if the measurements are correct, should extend about 1/4 in. above the collar.  The mineral wool, JJ, Fig. 4, is then packed down inside the collar, until it is within 1 in. of the top.  This will allow the plate, Fig. 1, to rest on the wool and the ends of the glass tubes, GG, Fig. 4, to project through the holes D and A of the plate, Fig. 1.  The rim of the plate should be level with the top edge of the collar.  If asbestos is used, the sheets should be cut into disks having the same diameter as the inside of the collar, and holes cut to coincide with the holes D and A of the plate.  The small scraps should be dampened and made into pulp to fill the space H, Fig. 4.  The plate, Fig. 1, is held to the base by two screws which are run through the holes BC and take the position shown by DD, Fig. 4.

The two binding-posts are attached on the base at D, Fig. 2, also the switch B and the fuse block C, holes being bored in the base to make the wire connections.  The reverse side of the base, with slits cut for the wires, is shown in Fig. 3.  The points marked BB are the glass tubes; AA, the holes leading to the switch; and C, the fuse block.  The wires run through the glass tubes GG, Fig. 4, are allowed to project about 1 in. for connections.

The best way to find the correct length of the resistance wire is to take a large clay or drain tile and wind the wire tightly around it, allowing a space between each turn.  The tile is then set on its side with a block or brick under each end.  It should not be set on end, as the turns of the wires, when heated, will slip and come in contact with each other, causing a short circuit.  When the tile is in place, a short piece of fuse wire is fastened to each of its two ends.  A 5-ampere fuse wire is about strong enough.  A connection is made to these two wires from an electric-light socket.  The wire will get hot but probably remain the same color.  If this is the case, one of the feed wires is disconnected from the fuse wire and gradually moved farther down the coil until a point is found where the resistance wire glows a dull red.  This point marks the proper length to cut it, as the wire should not be allowed to become any hotter.  If the wire gets bright hot when the current is turned on, more wire should be added.  The wire is then made into a long coil by winding it around a large wire nail.  The coils should be open and about 1/8 in. apart.