muslin, of standard one yard width, will be
needed. The forty-one ribs are each 4 feet long, and
1/2 inch square. A roll of No. 12 piano wire, twenty-four
sockets, a package of small copper tacks, a pot of glue,
and similar accessories will be required. The entire
cost of this material should not exceed $20. The wood
and cloth will be the two largest items, and these should
not cost more than $10. This leaves $10 for the varnish,
wire, tacks, glue, and other incidentals. This estimate
is made for cost of materials only, it being taken for
granted that the experimenter will construct his own
glider. Should the services of a carpenter be required
the total cost will probably approximate $60 or $70.

Application of the Rudders.

The figures given also include the expense of rudders,
but the details of these have not been included as the
glider is really complete without them. Some of the best
flights the writer ever saw were made by Mr. A. M. Herring in a
glider without a rudder, and yet there can
be no doubt that a rudder, properly proportioned and
placed, especially a rear rudder, is of great value to the
aviator as it keeps the machine with its head to the
wind, which is the only safe position for a novice. For
initial educational purposes, however, a rudder is not
essential as the glides will, or should, be made on level
ground, in moderate, steady wind currents, and at a
modest elevation. The addition of a rudder, therefore,
may well be left until the aviator has become reasonably