CLAYS OF KEW YOKK 685 



If the clay treated with the barium chlorid is used at once, no 

 efflorescence will result, either on the unbumed or the burned brick, 

 but if tlie clay thus treated is allowed to lie for any length of time, 

 large quantities of iron pyrite may be decomposed with the forma- 

 tion of additonal sulfates. It frequently happens that the discolora,- 

 tions on bricks appear near the edges and corners. This is due to 

 the fact that the waters evaporate most readily from these points. 

 The more quickly the water is evaporated, the less will be the 

 quantity of soluble deposit on the surface. Incrustations which 

 appear during drying are found more commonly on bricks made 

 from very plastic clays, and which owing to their density do not 

 allow the water to evaporate quickly. In sandy clays, the in- 

 crustation is at a minimum. This explanation is believed to account 

 for the appearance of efflorescence on the surface of pressed bricks 

 more than on rough surfaces. 



Cost of production 



This item varies considerably, depending on a variety of circum- 

 stances, such as the method of manufacture employed, cost of labor, 

 locality, etc. Brick manufacturers are generally unwilling tO' give 

 information on this subject, and the figures given, therefore, can 

 only be considered approximate. The use of improved machinery 

 and methods will often lower the cost of production considerably, 

 but this generally requires a much greater outlay of capital than 

 seems to be in most instances available. By the hand power method 

 the cost of manufacture is $3.75 to $4 a thousand delivered at tho 

 yard. On Long Island, where the soft mud process is almost ex- 

 clusively used, the cost is said to be $3 a thousand delivered at the 

 yard. Hudson river manufacturers quoite the cost at $5 a thousand 

 delivered in jSTew York city; this figure includes $1.25 for trans- 

 portation and 25c a thousand for commission. 



The brick yard is usually owned by the manufacturer but the 

 clay bank is worked on one of two bases: 



1 The manufacturer owns the bank. This is by far the best and 

 most profitable arrangement. 



