REMARKS ON BRICKS 151 



Permeability. — On account of the peculiar construction of the 

 Croton aqueduct there are several points at which a considerable 

 pressure is exerted on the bricks and a consequent permeation of 

 the water throuo-h them. A number of tests have been made by 

 A. W. Hale, engineer on the aqueduct, and a full description of the 

 apparatus and method used is given in pp. 17 and 28, Eng. Kecord, 

 1890. Thebricks tested were the Anchor brand of Croton Landing, 

 !N^. Y. It was found that with 80 pounds pressure per square inch, the 

 average percolation through a brick two and three eighths inches 

 thick, was equal to 12 and 3-12 cubic inches per square inch of 

 surface, per hour. The maximum percolation was 40.44, and mini- 

 mum was 4.02 cubic inches. From these experiments Mr. Kale 

 drew the following conclusions. 



That the percolation through a brick under constant pressure, 

 diminishes as the pressure is prolonged. 



That the diminution of percolation under constant pressure is 

 less and less rapid as the flow is continued and linally becomes 

 constant. 



Paving brick 



The paving brick industry, although in its infancy, gives indica- 

 tion of rapid growth in the near future. In the western states 

 many cities are paving their streets with brick. In this state 

 brick pavements have been introduced in the following cities, 

 Binghamton, Lockport, Buffalo, Rochester, Syracuse, Troy, 

 Watertown, Ithaca, Corning, Elmira, Dunkirk, Jamestown, Tona- 

 wanda and Niagara Falls. There are only four factories ia New 

 York state which furnish paving brick, and up to the present 

 time many of the pavers used in the state have been obtained 

 from West Virginia and Ohio. It was formerly thought that only 

 fire clays should be used in the manufacture of this product, but 

 this idea is being abandoned, for there are many clays which are 

 refractory enough for a fire brick which makes most excellent 

 pavers. 



In order to make a good paving brick the clay should be one 

 which will hold its shape at a heat sufficiently high to cause thor- 

 ough "vitrification", (as brickmakers call it.) It should shrink 

 evenly in burning. It should be tough but not brittle, and with- 

 stand abrasion. It should also withstand considerable pressure; 



