KBMAKK8 ON BRICKS 149 



the clay from which the brick is made and the method of drying 

 and burning. 



2. It should be of fine compact and uniform texture, quite hard 

 and give a clear ringing sound. The compactness and uniformity 

 of texture, which greatly influence the durability, depends 

 mainly on the method of moulding. Hand machines produce 

 brick of homogeneous character. Tempered clay bricks are 

 denser interiorly. Dry clay machines produce a thoroughly 

 homogeneous and dense brick it is claimed. 



3. It should not absorb over 10 or 15 per cent, of water. A 

 simple method of testing this is to place the brick for 2i hours 

 in a bucket of water, weighing it before and after immersion. 

 The increase of weight is the amount of water absorbed. This 

 applies only to hard burned bricks. A salmon or green brick 

 will absorb much more. 



4. It should have a specific gravity of 20 or more. 



5. It should have a crushing strength of not less than 3000 

 pounds per square inch. 



The manner of making crushing tests is described under the 

 head of paving brick. 



Building brick may be divided into three kinds, arch, red and 

 salmon. 



Common bricks run quite uniform in size. There is a difference 

 of perhaps three sixteenths inch between a brick made in a new 

 mold, and one^made in a mold which has been used one or two 

 seasons. The dimensions of an average sized common brick are 

 about two and one quarter by three and three quarters by eight 

 and one quarter inches. We give below a table of the sizes of 

 common brick manufactured in this state together with the 

 amount of water they absorbed when soaked for 24- hours. 



