DRAINAGE METHODS FOR COUNTY ROADS. 77 
pyrites, or any other minerals which are known to cause slaking or disinte- 
gration of the tile shall be valid ground for rejection, unless satisfactory proof 
be submitted that the tiles are permanent and durable, and that the objection- 
able minerals are not present in quantity or condition to work damage. 
The physical tests of the tile shall include strength and absorption tests made 
in accordance with the standard specifications for drain tile adopted by the 
American Society for Testing Materials in 1916. The average ordinary sup- 
porting strength shall be not less than 800 pounds per linear foot. The average 
absorption by the boiling test shall not exceed 11 per cent for shale and fire- 
clay tile, or 14 per cent for surface-clay tile. Tile made of mixed clays shall 
conform to the absorption requirements for surface-clay tile when the propor- 
tion of surface clay is 75 per cent or more, and to the requirements for shale 
and fire-clay tile for other proportions. 
All tile shall be inspected visually (1) to cull and reject imperfect individual 
tiles, and (2) to determine whether the tales, independently of meeting the 
chemical and physical requirements, comply with the specifications of general 
properties, especially as stated! hereinafter. 
The bore of all tile shall be approximately circular, the tile shall be approxi- 
mately straight, and the ends of the tile shall be so regular and smooth as to 
readily admit of making joints hj turning and pressing together adjoining 
tile. 
The sizes of drain tile shall be designated by their interior diameter. 
The tile shall have a minimum length of 12 inches. 
The tile shall be substantially uniform in structure throughout, as deter- 
mined by an examination of fractured surfaces. 
The tile shall have a clear ring when stood on end and while dry tapped with 
a light hammer. 
The tile shall be reasonably smooth on the inside. 
The tile shall be free from cracks and checks extending into the body of the 
tile in such manner as to decrease the strength appreciably. Tile shall not be 
chipped or broken in such manner as to decrease the strength materially or to 
admit earth to the drain. 
The tile shall not vary from straight by more than 5 per cent of its length. 
The maximum and minimum diameters of the same tile, or the average diam- 
eter of adjoining tile shall not differ by more than 85 per cent of the thick- 
ness of the" tile wall. The average diameter of a tile must not be less than 95 
per cent of the specified diameter. Exterior blisters, lumps, and flakes which 
do not weaken the tile and are few in number will be allowed, but only when 
their thickness does not exceed 25 per cent of the thickness of the tile wall and 
when their diameters do not exceed 20 per cent of the internal diameter of the 
tile. 
The vendor may appeal from decisions of the inspector on questions of 
strength or structure when such decisions are based on visual inspection alone, 
in which case the point at issue shall be determined by standard physical 
tests, the cost of which shall be paid by the appellant if the inspector was 
right, or by the purchaser if his inspector was in error. 
CEMENT OR CONCRETE TILE. 
Wherever cement or concrete tile is called for the tile used shall be equiva- 
lent in all respects to the quality and strength of clay drain tile, and shall con- 
form to Specification C4-14 of the American Society for Testing Materials. 
