[ ¢z14 J 
eus and rotative motion, which itfelf is more extenfively ufeful 
than any other, and from which every modification of motion 
can be eafily obtained. 
Tuts machine confifts of three principal parts, the wheel, 
reprefented fig. 1; the cafe, fig. 2, and the , condenfer, which is 
the fame with that ufed in Mr. Watts’s engine, and requires 
no defcription. The wheel, fig. 1, has a broad flat edge, a 0, 
which is truly circular and fmooth; at equal diftances on this 
edge are placed eight folding clacks or valves, bc de fght; 
thefe are attached to the wheel by~ fmall moveable joints, 
which are fo contrived that when fhut they range exactly with 
the furface of the edge of the wheel, and are capable of open- 
ing half way, but no: more: For inftance, the valve a 2 m 4, 
has a joint at 7 m, which. will permit it to open through. the 
arch 6 & J, until it arrives at the fituation / m, but no) far- 
ther. Thefe joints are fo pliant that in the revolution of the 
wheel the valves will fal! open when they defcend near the 
level of the axis: and when they. afcend above it they will 
fhut, by their own gravity. 
Tue cafe of this wheel is. reprefented, fig. 2. The fides of at 
are at fuch a diftance from each other as that the wheel will 
exadily fill up the aperture 2 4, and the caps ¢ and @ are fo 
fitted that the edge of the wheel will come in’ clofe conta& 
with them. ‘This cafe is fo much deeper than the wheel,’ that 
the wheel, when fixed in it, leaves a femicitcular vacancy, 
e f g h, below it, which is exaélly filled up by the valves . 
of the wheel when extended. 7 is the tube to admit the 
fieam, 
a 
