214 The Philippine Journal of Science i9i6 



because the vitrification range is so short. It commences to 

 vitrify at about cone 4 and is completely fused at cone 9. The 

 tensile strength is much lower than that of clay 1 (12.2 kilograms 

 per square centimeter) . 



No. 3. All the physical tests made indicate that this sample 

 is worthless for either building or paving brick. It has a very 

 high shrinkage, poor drying qualities, and practically no tensile 

 strength. The test bricks crack to pieces in the kiln. 



No. 4. This clay is very plastic and could not be used for 

 any class of ceramic work unless it was mixed with some inert 

 subtance. The test bricks crack to pieces on drying. 



No. 5. The drying qualities are good. It does not crack, but 

 warps to some extent. It has practically no tensile strength. 

 It begins to vitrify at about cone 1, but cracks to pieces at 

 cone 7. It seems to have none of the qualifications of a paving- 

 brick material, but could possible be used in making building 

 brick. Its usefulness for this purpose would depend largely 

 upon the extent of its contamination with stone. If this con- 

 tamination continues very far back from the outcrop, the labor 

 required to purify it would probably be prohibitive for building- 

 brick manufacture. 



No. 6. Carbonates are present in sufficient quantity in this 

 material to prohibit its use if fired above cone 03. The test 

 bricks fired below that temperature seem satisfactory for building 

 brick. If building brick were made of this sample and burned 

 in a kiln heated with coal, considerable care would be necessary 

 to avoid too high temperatures. The test bricks break up at 

 about cone 03 on account of the evolution of carbon dioxide and 

 fuse completely at cone 05. The tensile strength is 21.7 kilo- 

 grams per square centimeter. The working and drying qualities 

 are satisfactory. Some of the test bricks soaked in water over- 

 night showed no signs of cracking or disintegration. 



No. 7. There is some contamination of stone in this material, 

 and its drying qualities are poor. It appears worthless for 

 either building or paving brick. The test bricks lose shape 

 before reaching cone 1. 



No. 8. The working behavior and drying qualities of this 

 material are good. The tensile strength of the briquettes is 

 exceptionally high (31.3 kilograms per square centimeter). It 

 seems satisfactory for building brick if burned at about cone 05. 

 It has too low a fusing point for a satisfactory paving brick 

 if worked alone. Its high tensile strength leads me to believe 

 that it could be advantageously mixed with some inert siliceous 

 material. 



