6 76 NEW YOKK STATE MUSEUM 



The kiln is now " hot " and the bricks commence to shrink or 

 " settle " and all the platting is turned down. Up to this point 

 care must be used to increase the heat gradually. The bricks now 

 get their heaviest heat, and the oxids of iron are changed to the 

 anhydrous peroxid, giving the bricks their red color. If the heat 

 in the arches is too great the bricks run, stick together or become 

 distorted and cracked. After the firing has been done the doors 

 are all closed and plastered over to prevent any air from entering. 



If the bricks are put into the kiln before they are sufficientlT 

 dried, or if they are heated too quickly, they are liable to crack. 



In the case of coal, grates have to be put in a few inches above 

 the level of the floor, and for oil, burners are needed. 



After a kiln of bricks has been burned, the ends of the arch 

 bricks are often black, caused by the particles of dust and carbon 

 which have been carried upward sticking to the brick when they 

 were in a soft condition, due to the high degree of heat. 



As to the action of the coal dust in the brick. At first while 

 the brick contains water, there is no access for the air to the particles 

 of coal. However, as the firing proceeds, the water is driven off, 

 leaving the brick porous, allowing the air to enter for the com- 

 bustion of the coal. Particles of lime and lumps of clay cause a 

 splitting of the brick. Insufficiently burnt bricks are called 

 " pale " and sell for $3,75 a thousand. 



The kilns take several days to cool, and, when cool, the bricks 

 are put on wheelbarrows, and taken to the freight cars, or barges, 

 and then shipped to the market. If the kiln shed is not situated 

 along the dock, the barrows are put on a car, which is run down 

 a track to the scow. The time of burning is from five to seven 

 days with wood and four to five days with oil. The cost of burn- 

 ing with wood is 60 to Y 5c a thousand brick, and with coal the 

 cost of burning is 40 to 50c. Burning with wood is the cheapest 

 method as far as implements are concerned. With coal there is the 

 cost of grates and with oil there is a royalty of $1.60 to be paid on 

 every burner. The latter is, however, the cheapest method as 



