36 



GENERAL DISCUSSION OF CLATS. 



Fusion 



The theory of these pyramids is that the cone bends 

 over as tlie temperature approaches its fusing point, 

 and when this is reached, the tip touches the base. If 

 the heat is raised too rapidly, those cones whicli con- 

 tain much iron swell and blister and do not bend over, 

 and the best results are obtained by the slow softening 

 of the cone under a gradually rising temperature. 



For practical purposes these cones are considered 

 sufficiently accurate. 



In actual use they are placed in the kiln at a point 



