13 FARM BUILDINGS IN SOUTH AFRICA 



cut to about 4-foot lengths. In order to stoke, the ends of the fuel 

 chambers must be opened; they should be re-closed immediately after- 

 wards. The clamp should be kept burning until it shows red-hot at 

 the top. Hard-wood logs from trees such as Wattle, Mimosa, Red-thorn, 

 and some of the Gums, are suitable as fuel. 



Quality and number of Bricks to be expected from a Clamp. — On 

 account of unequal firing the bricks burned in a clamp will vary in 

 quality. In general, those nearest the fire, or in the heart of the clamp, 

 are the hardest. Insufficiently burned bricks may be reburned in a future 

 clamp, being placed near the outside thereof. 



From the clamp illustrated by Fig. 8, for coal-firing, we might reason- 

 ably expect to obtain over 35,000 good bricks or so-called " reds " ; while 

 from the clamp described and illustrated (Fig. 9) for wood-firing we might 

 hope to procure nearly 20,000 reds. 



Soft bricks may be used for inside or party walls, and in places where 

 little weight comes upon them. Hard-burned bricks should be reserved 

 for foundations, outside walls, and places in which they are called upon 

 to resist great weight. 



The bricks forming a clamp should be carefully and evenly laid, so as 

 to insure the production of shapely well-burned bricks. 



Tests for a good Brick. — A good burnt brick should be regular in 

 shape, with flat parallel surfaces, and sharp right-angled edges. 



It should emit a clear ringing sound when struck against another good 

 brick. 



When broken it should show a compact uniform structure, hard and 

 somewhat glassy, and free from air-bubbles. 



It should be free from cracks. 



It should not absorb more than one-sixth of its weight of water 

 when saturated. 



When set on end in a hydraulic press it should stand a pressure of 

 1100 lbs. per square inch before crushing. 



It is only after considerable experience, and with the best of materials, 

 that a brick conforming to the above tests can be produced, but no farmer 

 need despair of being able to make a burnt brick strong and durable 

 enough for ordinary purposes. 



Sun-dried Bricks. — Sun-dried bricks are made in the same way as burnt 

 bricks, excepting that the burning process is omitted. They can be made 

 of earth consisting almost entirely of clay and sand, without the presence 



