As the car shot to the basement Theo noticed a change in the appearance of the factory. On every floor they passed there was a hum of machinery and a glimpse of endless rows of china dishes; they stood on shelves; they covered tables; they were stacked one within another upon long counters. "Some dishes, eh?" Mr. Marwood laughed, reading the boy's thought. "I never saw so many in my life!" "You will see many more before you are through," remarked his companion. The elevator brought up with a jerk. "Here we are!" exclaimed Mr. Marwood. "At least this is our way into the slip-house." He led Theo through a passage and across a court into the adjoining building. Here a white powder covered everything. Men who hurried by in overalls and caps were dusty as millers, their hands being coated to the finger tips with dried clay. Mr. Marwood stepped forward into the long, cement-floored basement and pointed to the tracks embedded in it. "It is on these tracks," he said, "that the cars come in and deposit their contents in the bins. The bins are of a pretty good size, you see. They measure about sixteen by thirty-two feet, and each one will hold eight car-loads of clay. After the different kinds of clay are unloaded and placed in their respective bins, the proper combination for specific varieties of porcelain must be weighed out and mixed in the 'blungers,' as we call the mixing tanks. Now this body formula, or clay combination, is not entrusted to the ordinary workman. It is kept secret. Therefore we have on the trucks that carry the clay between the bins and the blungers what we call charging-scales, which weigh automatically each ingredient in the compound without betraying it to the loader." "That is pretty clever," replied Theo. "Yes, it is a very ingenious device," Mr. Marwood agreed. "The blungers in which the clay is mixed are over there. You can see them--those great machines near the centre of the floor. They are heavy steel tanks lined with vitrified brick, and in the middle of each one is a revolving contrivance, with steel arms and teeth that grind the clay up very fine and blend it thoroughly. While it is being mixed in this way water is added to it, and also a certain amount of powdered oxide of cobalt to whiten it." "Just as we put blueing in clothes," Theo ventured. Mr. Marwood assented. "This cobalt has already been pulverized and sifted most carefully, so there will be no particles in it, and so it will readily dissolve. After the clay mixture has had this mauling--for I can call it nothing else--the blunged compound, or slip, flows in liquid form into the sifter machines where it is strained through silk gauze or else a mesh of fine copper wire." "I shouldn't think you could ever strain such stuff," Theo declared.