Transcriber’s Note:

Obvious punctuation errors were repaired.

Both “overestimate” and “over-estimated” appear in the original text.

The following additional corrections were made to the text. The first passage is the original passage, the second the corrected one.

• Page 46:
  of items are discussed therein which, though simple, are
  of items are discussed herein which, though simple, are
• Page 48:
  the building up of a green by the superposition of blues, of
  the building up of a green by the super-position of blues, of
• Page 70:
  printing. At same time, it must be remembered that
  printing. At the same time, it must be remembered that
• Page 102:
  Bavarian limestone, 12
  Bavarian limestone, 1, 2
• Page 102:
  Embossing discs, 82, 83
  Embossing dies, 82, 83
• Page 103:
  Paper, enamelled, 61
  Paper, enamelled, 51
• Page 104:
  Extra powerful, 4
  Extra powerful, 11
• Page 104:
  Depolishing, 58
  De-polishing, 58