On the same plan, proximal cavities in the anterior teeth can be filled, and also buccal cavities in molars, especially where they extend to the occlusal surface. The cervical margin should be well covered with tin thoroughly condensed, thus securing perfect adaptation, and a solid base for the gold with which the filling is to be completed. Time has fully demonstrated that the cervical margin is most liable to caries, and here the conservative and preservative qualities of tin make it specially applicable. "Electrolysis demonstrates to us that no single metal can be decomposed, but when gold and tin are used in the above manner they are united at the line of contact by electrolysis. The surface of both metals is exposed to the fluids of the mouth, and the oxid of tin is deposited on the tin, by reason of the current set up by the gold; thus some atoms of tin are dissolved and firmly attached to the gold, but the tin does not penetrate the gold to any great extent." (Dr. S. B. Palmer.) This connection of the metals assists in holding the filling in place, but it is more likely to break apart than if it was all gold. After electrolysis has taken place at the junction, it requires a cutting instrument to completely separate the tin and gold. For filling by hand pressure, use instruments with square ends and sides, medium serrations, and of any form or size which will best reach the cavity. For filling with the hand mallet, use instruments with medium serrations, and a steady medium blow with a four-ounce mallet; in force of blow we are guided by thickness of tin, size of plugger, and depth of serrations, strength of cavity-walls and margins, the same as in using gold. The majority of medium serrated hand mallet pluggers will work well on No. 10 tin of one, two, or three thicknesses. If the tin shows any tendency to slide, use a more deeply serrated plugger. The electro-magnetic, and mechanical (engine) mallet do not seem to work tin as well as the hand mallet or hand force, as the tendency of such numerous and rapid blows is to chop up the tin and prevent the making of a solid mass, and also injure the receiving surface of the filling. In using any kind of force, _always_ aim to carry the material to place before delivering the pressure, or blow.