Lee Moor Firebricks are made from the refuse of china clay produced by the disintegration of felspathic granite (see p. 16), found chiefly in Cornwall and Devonshire granite.

A well-known variety of these bricks is manufactured at Lee Moor, near Plympton. They have a compact surface of a dull reddish-brown; are very hard and highly refractory.

Windsor or Hedgerly Firebricks are made from the sandy slate-coloured loam used for the manufacture of rubbers, and are of a red colour when burnt. These bricks consist chiefly of sand; they contain only 9 per cent of alumina, and a large proportion (4 1/2 per cent) of oxide of iron. They are unable, therefore, to resist very high temperatures.

The following Table shows the Crushing Strength, Weight when dry, and Absorptive Power of different classes of Firebricks : -

Resistance To Compression, Weight, And Absorption Of Firebricks

Description of Brick.

Dimensions of Specimen, in Inches.

Area exposed to crushing.

Average weight under which brick cracked.

Average force required to crush brick

Weight when dry.

Percentage of water absorbed.

Authority.!!

Length.

Breadth.

Thickness.

Stourbridge firebrick .

Sq. In.

Tons.

Tons.

Lbs.

9-08

4.4

2.47

39.9

25.0

50.9

7.2

9 5

L

Lee Moor do.

912

4.34

2.54

39.5

14.8

54.9

77

49

L

Newcastle do.

8.91

4.40

244

39.2

27.0

45.6

6.1

9 9

L

Dinas do.

8.92

432

2.44

387

28.0

49.0

6.9

9.3

L

Welsh do.

8.64

4.62

255

36.8

14.4

53.3

6.9

6.2

L