ng the angle formed by the two parts of the tail.

[Illustration: FIG. 165--Wind vane with dial.]

The rod should preferably be of brass, which does not corrode like iron. If
the uppermost 18 inches or so are of 1/4-inch diameter, and assigned a
bracket some distance below the one projecting from the top of the pole,
the remainder of the rod need not exceed 1/8 to 5/32 inch in diameter, as
the twisting strain on it is small. Or the rod may be built up of wooden
rods, well painted, alternating with brass at the points where the brackets
are.

[Illustration: FIG. 156.--Elevation and plan of vane.]

The Bevel Gearing.--Two brass bevel wheels, about 1 inch in diameter, and
purchasable for a couple of shillings or less, should be obtained to
transmit the vane movements to the dial arrow. Grooved pulleys, and a belt
would do the work, but not so positively, and any slipping would, of
course, render the dial readings incorrect. The arrow spindle (of brass)
turns in a brass tube, driven tightly into a hole of suitable size bored
through the centre of the post (Fig. 157). It will be well to fix a little
metal screen over the bevel gear to protect it from the weather.

[Illustration: FIG. 157.--Details of bevel gear and arrow.]

The Dial--This is made of tinned iron sheet or of 1/4-inch wood nailed to
1/2-inch battens. It is held up to the post by 3-inch screws passing
through front and battens. At the points of contact, the pole is slightly
flattened to give a good bearing; and, to prevent the dial being twisted
off by the wind, strip iron or stout galvanized wire stays run from one end
of a batten to the other behind the post, to which they are secured.

The post should be well painted, the top protected by a zinc disc laid
under the top bracket, and the bottom, up to a point 6 inches above the
ground level, protected by charring or by a coat of boiled tar, before the
dial and the brackets for the vane rod to turn in are fastened on. A white
dial and black arrow and letters will be most satisfactory against a dark
background; and vice versa for a light background. The letters are of
relatively little importance, as the position of the arrow will be
sufficient indication.

It gives little trouble to affix to the top of the pole 4 arms, each
carrying the initial of one of the cardinal points of the compass. The
position of these relatively to the direction in which the dial will face
must be carefully thought out before se