306 SELF-PACKING VULCANITE APPARATUS. 



never being removed from that position from the 

 time they have been tried in the mouth, we may- 

 say, until they are ready for wearing in the 

 mouth. With a certain amount of carelessness 

 we may, even in this mode of packing, have the 

 diaphragm ; but it is the fault of the manipulator 

 in not screwing up the clamp sufficiently. Acci- 

 dents may happen in going through this process 

 as they may in going through any other, if certain 

 points are not attended to ; but the action is 

 exceedingly simple, and my first year's apprentice 

 generally does all the packing .in the work-room. 

 From the time the teeth are modelled in wax, 

 until they come out of the vulcanizing chamber, 

 they do not require, as it were, skilled labour, 

 or, at least, very little of it. The frame of the 

 packing-machine is made exceedingly strong, and 

 in wrought iron, as a great deal more pressure is 

 required to force the rubber into the fine inter- 

 stices than might be generally supposed. The 

 plunger, instead of revolving and turning with the 

 screw, is coupled to the screw by a joint, so that 

 it is pushed straight down into the cylinder. The 

 cylinder has a side motion to enable it to receive 

 a fresh charge of material. The rubber may be 

 made up into blocks suited to the form of the 

 cylinder, not unlike a very large cartridge, so that 

 the cylinder contains enough for eight or nine 

 cases. If we have three or four cases to pack, 

 after the cylinder is once heated, half a minute is 



