est; 



Report of the State Geologist. 



Continuous kilns are used at several localities, and while they work 

 fairly well, still they can hardly be considered to have completely emerged 

 from the experimental stage. 



In burning paving brick the temperature is gradually raised to the point 

 of vitrification and the kiln held at this temperature for several days in order 

 to allow the heat to thoroughly penetrate each brick and cause it to get its 

 maximum shrinkage. The kiln is then cooled very slowly to anneal the brick 

 and give a hard, tough product. 



The temperature attained in paving-brick kilns varies, but it may be said 

 in general to vary from 1,700° F. to 2,000° F. In experiments made by 

 Professor Orton, Jr., of the Ohio Geological Survey, the temperatures of 

 paving-brick kilns when at their best heat varied from 1,800° F. to 1,920° F. 

 In the New York shales tested it was about 2,100° F. 



Requisite Qualities of Paving Brick. 



As paving brick are laid in streets, they are subjected to considerable 

 wear and tear, which they should be able to withstand if of good quality. 

 In order to determine by experiment in the laboratory whether a paving 

 brick possesses the requisite characters, certain standard methods of testing- 

 have been devised. 



Recently the National Brickmakers Association appointed a committee 

 to carefully go over the various methods of brick testing and draw up a set 

 of standard specifications. The tests considered were the rattler, absorption, 

 cioss-breaking and crushing test, and the recommendations of the committee 

 were as follows : 



Specifications for Abrasion Test. 



I. Dimensions of the machine. The standard machine shall be twenty- 

 eight inches in diameter and twenty inches in length, measured inside the 

 rattling chamber. Other machines may be used, varying in diameter between 

 twenty-six and thirty inches, and in length from eighteen to twenty-four 

 inches, but if this is done a record of it must be attached to the official report. 

 Long rattlers may be cut up into sections of suitable length by the insertion 

 of iron diaphragms at proper points. 



II. Contraction of machine. The barrel shall be supported on trunnions 

 .it either end; in no case shall a shaft pass through the rattling chamber. 

 The cross-section of the barrel shall be a regular polygon having fourteen 

 sides. The heads and staves shall be composed of grey cast iron, not chilled 



