CLAYS OF NEW YORK 753 



line of wear produced when brick are laid witli sand filler in tlie 

 street ". 



The charge adopted by Mr Jones consists of 150 pounds of cast- 

 iron cubes, each ^ inch each way, and weighing .87 of a pound. 

 The rattler is revolved 3000 times. Bricks which are considered 

 standard lose 5^ of weight ; these would be condemned if found 

 on the street. 



Mr Jones analyzes the action of his rattler as follows. First, the 

 ascending side of the rattler carries up part of the charge of cubes, 

 imparting to them its velocity. When carried beyond the center 

 they are thrown toward the opposite side of the rattler chamber, 

 and therefore strike on the unprotected surface of the brick, chip- 

 ping the edges, cutting into the surface, and doing all that the calks 

 of a horse's shoe can do. Second, as only part of the charge of 

 cubes can be carried upward by the ascending side of the rattler 

 chamber, the rest slide and roll over the surface of the brick at 

 the lowest point, grinding and wearing them away. 



Thus we have : 



1 Brick in position as in the street 



2 Continual raining of iron cubes on the surface — analogous to 

 the shock of horses' feet 



3 Attrition and rolling wear as of wagons 



4 Wear confined to the narrow surface of the brick — as in the 

 street 



5 Uniform and standard abrading material 



6 Like conditions for testing any material from fire clay to 

 shale 



7 Influences of change of form minimized 



8 Weight, cross-section, form and structure estimated at true 

 value, as they are all reduced to surface and resisting quality of 

 material. 



As only one edge is subjected to abrasion, it is possible to 

 multiply the loss of weight suffered by one brick by the number 

 required to lay a yard and thus ascertain the number of pounds 



