[ 7 5 ° 3 
Line E H, and to crofs it, in cafe of high Winds, 
for fecuring the Papers down, on Three Sides ; and . 
a Fourth might be added, but there is feldom any 
Occafion for it. 
To the Centre of the Table underneath, is fixed a 
brafs Socket, fo truly made, that the Table may, 
when fet, turn round truly horizontally : And a Ma- 
chine, cafed with Glafs, in which a Plumbet hangs, 
to fet the Table level; or the parallel Plates, and 
glafs Tubes of Spirit of Wine, may be ufed, to fet it 
horizontal, as any one fees Occafion to fanfy them. 
To any one of the Four Edges underneath, is 
ferewed a Box and Needle, fet to the Variation. 
There belongs to this Inftrumenr, a ftrong Three- 
legged Staff, and an Index with plain or telefcopical 
Sights, near Two Feet long. 
The. Papers, or Charts, for this Table, are to be 
either a thin fine Paftboard, fine Paper pafted on 
Cartridge-paper, or Two Papers pafted together; cut 
as exadly fquarc as is poftible, each Side being nearly 
1 6 Inches and an half long, juft as they may (lide in 
eafily between the upright Part and under the flat 
Part of the Holders. 
Any one of thefe Charts will be put in the Table 
any of the Four ways, be fixed, taken our, and 
changed at Pleafure: Any Two of them may be 
joined together true on the Table, if you make each 
of them meet exact at the Line LM, whilft near one 
half of each will hang over tre Sides of the Table; 
or by crefling and doubling each, the Whole of them 
will be within the Tabic. And if Occafion fhould 
happen, as feldom it docs, by crefling each Paper 
both Ways through the Middle, Four of them may 
be 
