Fig. 133. THE MAGIC DRUM.
Drum, Electric.
A drum with a mechanism within for striking the head with a hammer or
some equivalent method so as to be used as a piece of magical apparatus.
In the one shown in the cut a sort of telephone action is used to
produce the sound, the electro-magnet D and armature being quite
screened from observation through the hole. (See Fig. 133) A ring, C,
shown in Fig. 133, with two terminals, the latter shown by the unshaded
portions a a, and a suspending hook E, also with two terminals, and two
suspending conductors A, B, carry the current to the magnet. A sudden
opening or closing of the circuit produces a sound.
Dub's Laws.
1. The magnetism excited at any transverse section of a magnet is
proportional to the square root of the distance between the given
section and the end.
2. The free magnetism at any given transverse section of a magnet is
proportional to the difference between the square root of half the
length of the magnet and the square root of the distance between the
given section and the nearest end.
Duct.
The tube or compartment in an electric subway for the reception of a
cable. (See Conduit, Electric Subway.)
Dyad.
A chemical term; an element which in combination replaces two monovalent
elements; one which has two bonds or is bivalent.
Dyeing, Electric.
The producing mordanting or other dyeing effects on goods in dyeing by
the passage of an electric current.
Dynamic Electricity.
Electricity of relatively low potential and large quantity; current
electricity as distinguished from static electricity; electricity in
motion.