4 BULLETIN 246, U. S. DEPARTMENT OF AGRICULTURE. 



inches in cross section, and the brick are formed by cutting through 

 the column, by means of an automatic device, at intervals of about 

 3^ inches. For " end-cut " brick the column has a cross section 

 approximately 4 inches by 4r| inches and is cut into sections about 

 10 inches long. 



Paving brick, whether end or side cut, have usually in the past 

 been re-pressed. This process smooths the surfaces, rounds the cor- 

 ners, and forms on one side of each brick small lugs which serve 

 to produce uniform spacing between the successive courses of the 

 pavement. Suitable lugs may also be formed at the time the brick 

 are cut, and the process of re-pressing is then omitted. Much dis- 

 cussion has taken place as to which of these methods produces the 

 better brick, and each method has many advocates. Entirely satis- 

 factory pavements have been made from both re-pressed and unre- 

 pressed brick under widely different conditions, and it is very doubt- 

 ful if the failures which have been observed in connection with either 

 type could rightfully be attributed to this particular feature in the 

 process of manufacture. 



Special shapes, such as nose brick for use next to car tracks, and 

 hillside block, which have one side thicker than the other and which 

 are used on steep grades in order to give the pavement a rough sur- 

 face, may be made either by special die or special re-press molds. 



The next step in the process of manufacture consists in drying the 

 brick. In a properly systematized plant the brick are stacked upon 

 drier cars as they leave the presses in such manner as to permit a 

 free circulation of air between them. The loaded cars are imme- 

 diately run into a tunnel dryer, the temperature of which is main- 

 tained at about 100° F. at the entering end. As cars containing 

 " green " brick enter one end of the tunnel, which is usually more 

 than 100 feet long, other cars containing dry brick are being removed 

 at the opposite end. Air circulation in the dryer is effected by means 

 of fans or high stacks. During drying the brick lose an amount of 

 moisture equivalent to from 15 to 20 per cent of their own weight. 



The brick leave the dryer ready for burning, which is the last and 

 undoubtedly the most important step in the process of manufacture. 

 Upon the burning depends largely the quality of the finished product, 

 and it requires the greatest skill so to regulate the temperatures and 

 firing periods as to obtain the best results from a given material. 

 Experience alone can demonstrate the manner in which the burning 

 must be modified in order to suit varying sets of conditions. The 

 kilns in which the burning is done are made of brick and are provided 

 with numerous furnaces. The brick are placed in the kilns so as to 

 permit a free circulation of the gases of combustion and the heated air. 



