Cellar (5) (Night guard’s room)
Look through the other room. It is dark there.
You can easily direct the light with an adjustable lamp and a mirror.
Eyeglasses can be used as converging lenses. (Page 5 of the book)
The secret heritage
of Professor Hatvani
Lock 2 - „Aurum, Cuprum,
Lock 3 - Portrait of a scientist
Lock 5 - There is only one truth
Lock 6 - Rubber bell
and bone pipe
PUZZLE: Rubber bell