CLAYS OF MIDDLESEX COUNTY. 455 



5. No. 2 stoneware clay. May develop a yellow-green ctain on 



weathering, but this disappears on firing, 3-4 feet 



6. Terra-cotta clay. Burns .buff. More plastic than layer 5. Vis- 



cous at cone 26-27, 4-6 feet 



7. Sand cemented by iron oxide, 6 feet 



The second grade of stoneware clay from this district is in- 

 cluded in the next class. 



SEMIREFRACTORY CEAYS. 



This class includes the lowest grades of fire clay found in the 

 Middlesex district as well as many other clays of similar refrac- 

 toriness, but known to the trade by other names, such as fire- 

 mortar clay, No. 2 stoneware clay, pipe clay, pressed-brick clay, 

 wad clay, terra-cotta clay, etc., as well as some purely local terms, 

 such as "blue top clay," "yellow top clay," etc., which have no 

 significance except to the clay miner. They fuse between cones 

 27 and 30 inclusive. 



Fire Clays. 



Most of these low-grade fire clays become viscous at cone 

 27. They are probably more widely distributed both geograph- 

 ically and geologically than either of the two' other grades 

 which have been described from Middlesex county. On analysis 

 they often show a higher percentage of fluxes as well as greater 

 sandiness. Their air shrinkage is somewhat lower than the No. 

 1 fire clays, and their tensile strength higher. 



Woodbridge. — One of these sandy clays is to be seen at locality 

 6 (Lab. No. 377), Anness & Potter's pit, and represents layer 4 

 of the following section, made September, 1901 : 



Section at Anness & Potter's bank, Woodbridge. 



1. Glacial till, 8-9 ft. 



2. Hollow-brick clay, 12 



3. Laminated sand and clay, '. 7 



4. Top-sandy clay, ; 5 



5. No. 1 fire clay, 3 



6. No. 2 fire clay, 3 



7- Bottom-sandy clay, 3-4 



8. Red-mottled clay, 14 



9. Poor clay and yellow sand, 



