MODE OF CASTING BEDS AND PALATES. 76 



and the top of the model are in perfect opposition, 

 and to keep the models in their central position 

 upon the top of the pedestal there is an iron plate, 

 with two screws to keep it fast ; and to make up 

 for the thickness of the ladle when the lead is 

 taken out of it, there is an iron ring inserted, 

 which makes up for the vacant space. By these 

 means the models cannot possibly shift, so that 

 every stroke of the hammer must be true, and 

 thus very satisfactory results are obtained. 



Mr. F. G. Harrington made the following com- 

 munication " On a mode of casting Beds and 

 Palates for Artificial Teeth in the new metal, 

 Aluminium ; also on improvements in Flat Mineral 

 Teeth." 



After stating that the new metal is the basis of 

 common clay, he said, — '* Like gold, aluminium 

 possesses the property of resisting the action of 

 all such acids as are likely to come in contact 

 with it in the mouth. Nitric and sulphuric acids, 

 or melted sulphur, do not appear to affect it in 

 the least!" In addition to which he exhibited 

 a piece which he had worn in his mouth night 

 and day for six months without its having under- 

 gone the least apparent change. These tests had 

 fully satisfied him that it could be placed in the 

 mouth with the most perfect confidence respecting 

 its durability^ freedom from taste, and everything 

 offensive. 



