( jo8 ) 
two Buttons fixed to it, which reft againft the fore Part 
of the Axis. 
To keep the Pillar from touching any of the Sides 
of the round Hole, in which it turns, a Cylindrick 
Sedor, containing about 65° or 70°, and about an Inch 
in Height, is cut out on the back Part of the Pillar, near 
the upper End D. In the fquare Angle of this Cavity 
is fix’d a thin Steel Plate 00, bent crofs the middle to 
the fame Angle. The internal angular Edge, between 
the two Parts of this Plate, lies in the Axis of the Pil- 
lar, and turns upon the harden’d Edge of a Wedgelike 
Iron, f\ whofe Bafe, or Board Part, is faften’d with 
two ftrong Screws on the Top of the Box, diredly 
behind the round Hole beforemention’d. 
The upper Parts of the Cheexs are ftrengthened by 
two Brackets, GG, leaving Room between them for 
the Bottom of the- Tube to touch the upper Edge of 
the fore Part of the Head. The hinder Part of the 
’Head is alfo hollow’d, in the Manner reprefented in the 
third Figure. 
The Head on its fore Part carries a flat Arm, M, 
Fig. I. about twenty feven Inches long, a little taper 
• towards the farther End, where it is four Inches broad. 
This is ftrengthened by a narrow Slip, glew’d edge- 
wife a longthe middle underneath, O, and aUb by a Brace 
or Stay, N, reaching from the turning Pillar to within 
nine Inches of the End of the Arm. The Stay paffes 
through a tranfverfe opening cut in the fore Part of the 
Box, P, which is long enough to allow room for a fuf- 
ficient Motion of the Pillar round its Axis. 
On the other End of the Bottom Plank, tranfverfely 
to its Length, is erefted a Board about twelve Inches 
wide, and twenty fix or twenty feven high, Q_, the 
Top of it reaching within an Inch and an half of the 
under Side of the Arm. -This Board is held firm in its 
I Polition 
