[ 749 3 
or a brafs Frame round it, to prevent its warping, 
and, as much as poflible, fhrinking and fwelling. 
Within Six-tenths of an Inch of Two of its op- 
polite Sides (and parallel to them and one another) 
are Two Grooves E F, GH, cut on the Face half an 
Inch deep, to let in Two brafs Holders in the Shape 
of NO, Fig. 2. which are each of one Piece of call 
Brafs, likcTwo brafs Rulers, joined together at Right 
Angles. The perpendicular Part is One-tenth and 
Three hundredth Parts of an Inch thick, as at d, half 
an Inch deep, and a little Ihorter at each End than the 
upper Parr, which is 17 Inches long, Three-tenths 
broad, and about Eight Parts of an hundredth of an 
Inch thick; about Two Inches and an half from each 
End of the Holder, are thick Parts or Bofles in the 
upright Piece, as at F and through which are 
Holes tapped, to receive the Skrews F S, which 
Screws go each through a brafs Plate as T and V> fixed 
by Rivets on the under Side of the Table, and little 
round Nuts (as at a and b ) put on them, to confine 
them to their Shoulders in turning in the Plates, that 
they neither rife nor fall j thefe Holders mull go eafy 
in the Grooves, to fink eafy and even with the upper 
Surface of the Table. Then, when the Screws enter 
the Holes of the Holders, by turning R and S at the 
fame time forward, the Holders will fall, and 
pinch down any Papers, <&c. that arc under them ; 
and, turning backward, will rife and releafe them. In 
the Middle of one End of the Table is a Groove, to 
receive the Brafs JV, which has the fame fort of Screw 
and Fixing as the other, to raife or fall it. But the 
Groove is quadrantal, that the Holder W may on 
Occafion be turned fo as to lie all on the outlide the 
5 E 2 Line 
