CLAYS OF NEW YOEK 647 



Rock face brick. Tkese are produced by trimming the edge of 

 a pressed brick -witli cbisel and bammer, in imitation of stone. 

 Tbeir beauty is a matter of individual taste. 



Pressed brick are nsnally molded eitber by the dry press, semi- 

 dry press, or stiff mud process. In tbe last case, they have to be 

 repressed. Tb© prevalent custom is to burn tbem in down-draft 

 kilns. 



Crushing strength of bricks 



Many of the bricks manufactured in ]^ew York show a crushing 

 strength which is far greater than is necessary, but some, spe- 

 cially common brick, often approach the limit pretty closely. The 

 succeeding tests made by different persons give the strength of a 

 number from different localities. 



The following are the results of some tests made by H. Wil- 

 liams M. E., at Cornell university, on bricks from ISTew York 

 state, made by different methods from the same clay. Half bricks 

 were tested in each case, and plaster of pans put between surfaces 

 of bricks and plates of machine. 



Ultimate strength 



rp.f „, Per square 

 '■°^^'- inch 



Pounds Pounds 



1 Wire-cut brick 59 800 3 385 



2 Eed brick, dry-clay process, Glens Falls ... 34 660 3 580 



3 Stiff mud, side cut, repressed, buff, Glens 



Falls 104 360 6 510 



4 Soft mud, repressed red brick. Glens Falls.. IIT 100 5 365 

 6. Dry pressed buff brick. Glens Falls 83 680 5 800 



6 Soft mud brick, W. W. Parry, Rome 115 300 4 4Y0 



7 Stiff mud, repressed, W. W. Parry, Rome.. 240 000 8 760 



