is secured to the mast which is
fixed into the body of the cart as shown. The sail is linen
fabric. There are two crosspieces to aid in keeping the sail
properly opened. The steering arrangement is through the rear
shaft. The shaft is pivoted as in a hand-propelled cart, and the
rod I extends from the middle connection of the shaft up to a
point where the person seated on the wooden frame can handle it.
There is a brake arranged by making a looped piece J and hinging
it as shown. This piece is metal, fitted with a leather face. The
cord K is pulled to press the brake. I marks the support for the
mast underneath the body of the cart. In a steady breeze this cart
spins nicely along the roads.

** Replacing Ball Bearings [415]

Never change a single ball in a bearing. Renew them all.

** How to Construct an Annunciator [416]

Oftentimes a single electric bell may be connected in a circuit so
that it can be operated from more than one push button. These push
buttons are usually located in entirely different parts of the
building and it is necessary to have some means of determining the
particular push button that was pressed and caused the bell to
operate. The electric annunciator is a device that will indicate
or record the various calls or signals that may be sent over the
circuits to which the annunciator is connected. A very simple and
inexpensive annunciator may be made in the following way:

Before taking up the construction of the annunciator it would be
best to make a diagrammatic drawing of the circuit in which the
annunciator is to operate. The simplest circuit that will require
an annunciator is one where the bell may be operated from either
of two push buttons. In this case the annunciator must be
constructed to give only two indications. Fig. 1 shows how the
various' elements of such a circuit may be connected. B is an
ordinary vibrating electric bell, M1 and M2 are the two
electromagnets of the annunciator, A is a battery of several dry
cells, and P1 and P2 are the push buttons from either of which the
bell may be operated.

When the push button P1 is pressed the circuit is completed
through the winding of the magnet M1 and its core becomes
magnetized. In a similar manner the core of the magnet M2 becomes
magnetized when the push button P2 is pressed and the circuit
completed through the winding of the magnet M2.

If an iron armature, that is supported by a shaft through its
center and prop