EXPERIMENT STATION BULLETINS. 359 



The tile comprising lot five, some of which were made from washed 

 and some from unwashed aggregate, showed considerable difference 

 in density, the finer material being removed in the one case by the 

 washing. None of these had been in place in the ground, but from 

 appearances one would conclude that they were well made and that 

 both would be reasonably durable ; although it is evident that the walls 

 of the unwashed sample Avould be less susceptible to the passage of 

 soil solutions — undoubtedly an advantage in drain tile. 



Lot six represents a small piece of tile taken from the yard of a 

 tile manufacturer in one of the larger cities of the State. This sample, 

 though small, was typical of the tile in the yard at that time and was 

 found to be exceptionally porous, the cementing properties being so 

 weak that particles could easily be rubbed oft". It does not seem possi- 

 ble that such tile could remain sound Avhen placed in the ground. 



Two indications of good quality in tile are high supporting strength 

 and low percentage of absorption. Tile which shows a small percent- 

 age of absorption is to be preferred in every respect to that which shows 

 Iiigh absorption. In making examinations to determine the absorption 

 it is necessary to dry tile at a temperature of 212 degrees Fahrenheit 

 until they show no further loss in weight. Tile Avill absorb their full 

 capacity of water within twenty-four hours after immersion. Tests have 

 shown that high strength and low absorption go hand in hand. 



