264 Scientific Intelligence. 
motion, equal to 150 turns a second. It is unnecessary to describe the 
apparatus for producing this motion, as any apparatus will answer that 
can be adapted to the pinion and will give the requisite rapidity. The 
center of the torus is occupied by a thin disk which carries a plate of 
glass with parallel surfaces or a metallic mirror, by means of which, 
the exact plane of rotation of the moving object ean be observed through 
the reflection of a distant mark. The torus and its axis are su 
by a cylindrical ring 6, b’, (fi di 
which is occupied by the axis of the torus. In this ring are the ¢ 
cal pivot-holes, g, 9’, in which the two points of the axle of the torus 
n play and be more or less restrained in their movement. Al 
the screws with pivot-holes, the ring carries the vertical screws, t, ¥, 
which in connection with the other horizontal screws, v, v’, serve to ad- 
two agate plates on a third ring, d, d’, (fig. 1,) the exterior member 
the system. 
The apparatus is brought into exact equilibrium, with the knife blades 
the ring which carries it always remaining horizontal, so that, like the 
other will cause it immediately to dip accordingly. The exterior ring 
its 
vertical diameter contains the arrangement for suspension. This ar 
rangement consists of a hook 0, on the upper side of the ring for a 
taching a thread of untwisted silk; this silk thread is protected 
a vertical tube (f, fig. 1) and is attached to a thumbscrew ™, whic 
serves to raise or let down the ring a little, as may be needed. _ 
The piece which carries the hook passes through a double pieces & 
whose upper part acts in fixing-the ring in its position; but : 
no friction as the' object is only to prevent a pendulum movement It 
the ring. On the lower side, this ring carries a conical point, g.¥ the 
moves in a pivot-hole without touching, the object of which like 
part g, is simply to prevent a swinging motion. ; with 
his apparatus is supported by a semicircle, p, having 4 vgnets 
thumbscrews, a, a’, for making it horizontal, so as to place the 
and the large ring in a perfectly vertical plane. | ‘cle 
The torus and its ring may be easily taken out from the outer oe 
to be adjusted to the apparatus employed for setting the torus 1 roe in 
att moment this rotation is obtained, the whole system 1S f the piaa 
of rotation soon become a great i 
pparent. : 
or the purpose of measuring the apparent motion of the a val 
cle (or rather the actual motion of the observer) a large ring Jevel 
to Mg ag minutes, bole 
with the knife blades; and there is a microscope having a Axe" 
adjusted to the eye-piece, for reading the smallest divisions. I hn 
iantieaten eee of the circle is easily shown to be pro” 
OL 3 lat itude ( zs ¢ . 
