ON PLATE-CASTING. ' 19 



tical men I feel assured that the specimens I have 

 the honour to lay before you will need but little 

 explanation. They are cast in loam. A core 

 or mould of loam or sand, with plaster of Paris, 

 hitherto presenting an objectionable roughness on 

 the surface of the metal, I am now endeavouring 

 to cast in a composition of blacklead, somewhat 

 in the same way that small iron articles are 

 cast ; and I hope to be able to compensate more 

 thoroughly for the contraction of the metal. The 

 plates appear to me sufficiently hard and tough." 



The plates exhibited were — 



Nos. 1, 2, and 3, of different thicknesses. 



No. 4, cast with bands, the burr cleared away 

 to fit it to the plaster model. 



No. 5, suction-plate. 



No. 6, strong plate with bands. 



No. 7, upper plate, with bands and caps for 

 decayed teeth. 



All of these were cast in silver. 



No. 8 was a plate cast in 18-carat gold. 



" They were cast by Mr. Corbett, of Denmark- 

 street, Soho. A wax model of the plate is fitted 

 to the plaster cast by means of a slight heat, 

 produced either by dipping the sheet of wax in 

 warm water, or directly by holding it to the fire 

 and effecting any joining necessary with a heated 

 wire ; the impression of the whole is taken in 

 sand or loam. The mould is sprinkled and 

 slightly dried, and the wax plate being replaced, 



c 2 



