C 114 3 
Tables fully difcovered. The Methods which commonly 
are ufed for obferving the Moment of Time, a i-e either by 
Dials, or by taking iTie Suns Altitude by day, or that of Stars 
by niglit ; or by obferving the Altitude and Az^imuth of the 
Sun or Stars ; or by the Tr unfits of the Sun or Stars through 
the Mrr/W//i;^, or the comeing of fome Circumsolar Scars in 
the fame Vertical with the Pole-Scar. All which Methods 
are attended with many inconveniences and difficulties, the 
which our Author believeth his Way will avoid ; at leaft 
the moft material ones, which commonly arife in the Prac- 
tife.For whereas Dials mult be very large, if there fhall be any 
divifion for Minutes made difcernable, fb the uncertainty of 
the Shadow caft from a large Gnomon renders them ufelefs 
for nicenefi, when alio their lervice is only by Day, and when 
the Sun fhineth. All which hindrances are taken off by this 
new contrivance of our Author, where alfb there is no need 
/ of any Calculation of Oblique Spherical Triangles, all being 
done by a plain and fimple Obfervation, and by the Additi- 
on and Subltraftion of two ar three feiall Numbers; and 
that to fuch exa£tncls, that not a quarter of a Minute, or 
1 5 Seconds fhall be vt^nting,performable alfb both by day or 
night. Defcribing tlierefore his Inftrumeat in the Chap, 
he tells, that the Contrivance confifleth in making a very 
large Horizonul Dial, adapted to the Latitude of the place 
where the Obfervation is to be made,capable of receiving di- 
vifions into minutes, and parts of a minute, fitted with ^ 
large, flirong, and double Gnomon : He calls that a double 
Gnomon^ that cafts the Morning Shadow fiom its Weftern 
Edge, and the after-noon Shadow from its Eaftern Edge,and 
the Noon-fliadow by its thicknefi. This Dial is to be fur-. 
niHied with two pair of Sights, or Rulers, one is toierveijOj 
the Morning,or for Stars on the Eaflern fide of the Meridian^ 
the other to ferve in the Afternoon, or for Stars on ^hq 
Weftern fide of the Meridian. Each of theie confifts of rwa 
moveable Rulers ; one he calls the Honz.ontd KuUr^ the o^, 
ther the Gnomomck^ or Stile-Ruler. Thefe two Rulers muft 
be 
