e quick reply. "Our finest grade of porcelain has
little or no phosphate of calcium, or ground bone, in it. But it is in
consequence very costly, and therefore to meet the demands of the
market we also manufacture a porcelain slightly strengthened with a
bone element. Nevertheless this is composed of such a wonderfully
blended body that it is as exquisite as any of the most beautiful
English wares. Personally I prefer it to a pure feldspathic china."

"My questions are all answered now," laughed Theo. "Shall we go up to
the clay-shop?"

They rang for an elevator and stepped in.

"Next floor, O'Keefe," said Mr. Marwood to the operator. "I am going
to teach this lad how to make dishes."

[Illustration]

CHAPTER XVI

DISHES, DISHES EVERYWHERE!

[Illustration]

"Clay," began Mr. Marwood as they went along, "can be shaped in any
one of several ways, you know: either by throwing; by turning; by
pressing it into hollow moulds; by shaping it by hand over another
type of mould; by pressing it into flat ware such as platters and
plates; by making it by machinery over moulds as is done by hand; by
casting it into the desired form; and by compressing it."

Theo looked puzzled.

"The list sounds like a long one," Mr. Marwood went on smiling into
the boy's troubled eyes, "but when you understand the processes you
will find that it is all much simpler than it seems. Before we begin
to investigate any of these methods, however, I want to say just a
word about the moulds over which, or inside of which, the ware is
sometimes shaped; for moulds are a very important feature both of
pottery and porcelain-making."

"What are the moulds made of?" was Theo's first question.

"I am glad you asked, for that is the vital matter," Mr. Marwood
replied. "Many materials have been tried with varying degrees of
success--plaster-of-Paris, alabaster, steel, gun-metal, and brass. Of
course what is necessary is a strong, firm, absorbent material. Clay
moulds break too easily, and also become saturated with water and lose
their shape; metal moulds, on the other hand, while most useful in
making wares decorated with fine, raised designs such as the Wedgwood
figures, fail to seep up the superfluous water. Therefore
plaster-of-Paris has proved the best medium for the purpose. Not only
does it retain its form, but it also takes up a certain proportion of
the moisture from the clay that is moulded inside or outside it."

"I understand,"