664 NEW YORK STATE MUSEUM 



The effect of a difference in velocity between tlie central and 

 outer portions of the clay stream is to produce a laminated structure 

 in the brick. Plastic clays laminate more than lean ones, and even 

 the same clay may laminate more with one die than with another. 

 Irregularity of clay supply may be still another cause. In conimon 

 brick laminations are less harmful than in paving brick; repress- 

 ing may at times obliterate them to a large extent. The 

 auger machine is extensively used at the present day, spe- 

 cially in the manufacture of paving brick. It has a large capacity, 

 60,000 brick being not an unusual output for 10 hours. The 

 capacity of the auger machine is often increased by causing two 

 streams of clay to issue from it, and certain machines are said to 

 have produced 150,000 brick a day. Plunger machines have a 

 capacity of 25,000 to 30,000 a day. 



Building brick are mostly side-cut, while paving brick are com- 

 monly end-cut. 



If the brick are to be facing, they are repressed, for the purpose 

 of straightening their edges and smoothing the surface. 



Dry clay process 



The use of this method in the United States dates back 15 or 20 

 years, to its introduction at Louisville, Ky. In 'New York it has 

 not been in use over nine years. There are five dry press in works 

 in the state. The clay after being dug is usually stored in sheds 

 to dry. When ready for use it is taken out and charged into the 

 disintegrator or dry pan, both of which have been described under 

 " Preparation of clay." 



After passing from the disintegrator the powdered clay is car- 

 ried by an elevator to the upper story, where it is discharged on a 

 long screen inclined at an angle of about 45°. The material 

 which has been ground fine enough passes through the sieve and 

 down into the hopper over the molding machine. The tailings fall 

 into a hopper at the lower end of the sieve and are carried back to 

 the disintegrator. 



