268 Description of the Rotaseope. 
axis, which of necessity winds up the supporting threads, into a spi- 
ral about the axis. When wound up, the whole is placed in a tall 
glass air-pump receiver, open at both ends and furnished witha 
plate, collar of leathers and hook at the upper end. This receiver 
is a frustum of a cone, and so large as to allow the wheel to run 
freely up and down without interfering with the sides. Having ex- 
hausted the air, the wheel previously wound up is detached from a 
hook that had prevented its descent and revolves slowly at first, and 
increasing in velocity according to the law of gravity, reaches at 
length the extent of the cords, and being arrested in its downward 
progressive motion at the moment it has arrived at the maximum ve- 
locity of rotation, begins at that moment to wind up the cord in the 
opposite direction about the axis ; while the whole wheel necessarily 
rises and at length reaches to very nearly the same height as that 
from which it had descended, when its momentum being lost, it again 
descends, and so continues to do for many minutes, until the mere 
rigidity of the cord has gradually destroyed all the momentum due 
to the first descent. Ihad frequently observed, when performing 
experiments with this apparatus, both in vacuo and in air, that by 
swinging the wheel while ascending or descending, there was 2 de- 
cided tendency to a particular arrangement in respect to the position 
of its axis, compared with that of the direction of oscillation. 
5. A carriage is often overset in turning a corner, OF describing 
a curve of short radius. Here the effect is produced sometimes with 
astonishing suddenness ; at other times the inner wheel, or that which 
according to the direction of the turn, is describing the smaller cite 
cle, rises from the ground and revolyes for a second or two on Its 
axle without touching the surface; and, if the motion be not 0° 
rapid, may possibly return and allow the vehicle to recover its por 
tion, and pursue its course. But if the wheel which is revolving ™ 
air have any considerable velocity, the body of the carriage will ap- 
pear to be overset by a force greatly superior to that which is due t0 
6. A disk of metal or other heavy substance, when projected <i 
‘the air by the hand, receiving at the same time a rapid rotary motion 
will sometimes be observed to perform singular evolutions in cera 
parts of its track. 
7. The accurate experiments of Mr. Hutton and others, 07 gi 
nery, have proved that a very great deflection of a cannon shot, o 
the direction of the piece, often takes place, amounting in some 
stances to an angle of about 15°. 
