62 
THE YOUNG SCIENTIST. 
"And wondering when I would make the 
one I promised you, eh, Master Harry? 
Well, fetch me the materials." 
Harry bounded off, returning in a few 
minutes with a strip of pine wood and a 
piece of rattan cane in one hand, and a ball 
of thick twine and a sheet of pink tinted 
paper in the other. 
"Shall we get it done to-day?" asked 
anxious Harry, as he laid the materials upon 
the table. 
'* That depends upon how our materials 
turn out. The first thing we must deter- 
mine is to make the very best kite we can 
from the materials we have, and next we 
must try to make it as quickly as we can." 
" What shape is it to be, Uncle?" 
"A good question, Harry; and since you 
want the best kite, it must, of course, be of 
the best shape. " 
" But what is the best shape?" 
"Let us see if we can find out. A kite 
flies when the pressure of the wind strikes 
it in a certain direction. You know this 
because of the position in which you fasten 
the twine to the belly-band. But let me 
make you a sketch that you may under- 
stand it better; there (Fig. 1) is a kite with 
Fig. 1. 
the string fastened to the middle of the 
belly-band. It stands, you see, upright, 
and the wind twies to blow it away without 
lifting it up at ail; but if you fasten the 
twine higher up, as in this sketch (Fig. 2) 
the kite will stand aslant, and the wind will 
lift it. You see then, Master Harry, that it 
is the direction in which the wind strikes 
the surface of the kite that causes it to fly." 
"Yes, Uncle, but if you fasten the twine 
as you have made it in the first sketch, the 
kite will sweep round and round, and some- 
times come down headforemost." 
Fig. 2. 
" That will always occur when the pres- 
sure of the wind is greater above the point 
of the belly-band, where the string is fas- 
tened, than if it is below. Suppose you 
were to fasten the twine below the centre of 
the kite, as in Fig. 3; then all the surface 
Fig. 3. 
of the kite above the point where the belly- 
band is fastened, would be acted upon by 
the wind in a direction to keep the kite : 
down to the ground, while only the surface | 
from that point to the bottom of the kite ( 
can serve to counteract this, even when the \ 
kite stands upright; but when it slants 
over, as in Fig. 3, all the surface of the 
kite is being blown by the wind down ' 
towards the ground. " ! 
"But why should it sweep round and 
round, Uncle?" ^ I 
" Because the surface above the fastening ! 
point of the belly-band tries to keep the 
top of the kite downwards, and the weight 
of the tail tries to keep it upright. The 
