DIAL. 
comes near the end of the arm, the breadth of it fhould be 
*ftill greater, fo as to be almott ois 5 d, on account of the 
diftance between the tips of the a 
e hours Ao) be placed on the arms, by laying down 
et the el to their pro- 
per places, on the fides of 7 arms as they are marked in 
Each of the hour fpaces fhould ie divided into 
fear equal parts, for the half hours and quarters » in the qua- 
drant ef; and right lines fhould be jae ee — di- 
vifion-marks in the quadrant, to the in 
order to determine the places thereon, alee the fubdivifions 
of the hours muft be marked. 
This is avery fimple kind of univerfal dial , 
made, and has a pretty uncommon appearance 
een on. 
Ls, Refraged, are {uch as fhew the hour by means of 
fone, refining tranfparent fluid. 
r ftick be fet up, or any point be affigned in 
fone ve eel or difh for the centre of the dial, let an ioe 
zontal dial be applied over the fame, affigning the meridian 
it is atl 
ing garden 
in diameter, and one-third inch in breadth. Ina 
point of this rim there is a hole, cneden which the fun- 
beams being received, make a lucid {peck on the concavity 
of the oppofite femicircle, which gives the hour of the day 
in the divifions marked therein. 
Thefe divifions are made by defcribing a circle, ( Plate IV. 
Sg. 34+) to reprefent the ring, and drawing an horizontal 
F; with this~ i 
sith a 
oa 
_o 
2) 
ad 
ao 
the VIIT and IV through 18° 8 and the VII and Vi 
sie 9° | This may be eafily calculated by the 
glo 
Bat it only holds good about the times of the equinox. 
T'o have the dial perform throughout the whole year, the 
hole is made moveable, and figns of the zodiac, or the days 
«f the month, are marked on the convex fide of the ring, by 
taking, e.g. ET and Eé (fg. 34 ) on each fide of E equal 
to double the fun’s oo when he enters any 
Tau r Pifc 
particular fign, as 
s of thefe the 
dial is re€tified for the time. It is evident, from a view of 
the figure, that E XII 3is= F E XI I= thealtitude of the 
fun in the equinox ; but T XII E is equal to the fun’s de- 
clination i . Taurus, becaufe it is an angle in the circumfer- 
ence ftan ding upon an arc, which is double the declination ; 
and therefore T XII 3 is ee - the meridian altitude when 
the fun enters Taurus; and a 
remedy this inconvenience, by making the concave furface of 
the ring wider, and deferibing upon it feven circles, the mid. 
dle one to reprefeat the equinottial, and the extremes the 
tropics ; and in thefe circles they have miei the forenoon 
and afternoon hours from a table of altitu 
o ufe it, put the moveable hole to the a ae: the month, 
or ae degree of the zodiac the fun isin; then fufpending it 
y the little ring, turn it towards the fun, till his rays, 
as before, point out the hour among the divilions on the in- 
ide. 
Univerfal or sight ae Diat, is a ring-dial, which 
ferves to find the hou e day i in any part of the earth; 
whereas the for ee cae to a certain latitude. Its 
fours fee Aelia in Plate 2. 35« 
"It confitts of tw 8 OF He civclee, from 
wo to fix 
inches in diameter, aaa ace breadth, &c. prop ee 
The outward ring, A, reprefeats the meridian of any pla 
you are at, and contains two divifions of go° each, diametri- 
cally oppofite to one another, ferving the one from the 
tor to the north, the other to the fouth pole. The inn 
ring hay anos equator, and turns exa@tly within the 
al » by means of two pivots in each ring at the hour 
II. 
Acrofs the two circles goes a thin reglet or bridge, with a 
curfor C, that flides along the middle of the bridge. In the 
curfor is a little hole for the fun to fhine through. The 
middle of this bridge is conceived as the axis of the world, 
and the extremities as the poles; and on the one fide are 
drawn the figns of the zodiac, and on the other the days of 
the month. On the edge of the meridian flides a piece, to 
which is fitted a ring to fufpend the inftrument by. 
In this dial, the divifions om the axis are the tangents of 
the angles of the fun’s declination, adapted to the femi- 
diameter of the equator as radius, and placed on either fide 
of the centre: but inftead of laying them down from a line 
of tangents, a fcale o 
then 434 of thefe parts may be laid down toward each end 
from the centre, which would limit all divifions on the axis, 
becaufe 434 is the natural taugent of 23° 29’. And this, 
by a nontus fixed to the fliding-piece, and taking the fun’s 
declan from an ephemeris, and the tangent of that 
declination from the table of natural tangents, the flider 
might be always fer true within two minutes of a degree. 
And this fcale of 434 equal parts might be placed right 
againft the 234° of the fun’s declination, on ra axis, inftead 
of the fun’s place, which is there of httle For thea 
the flider might be fet in the ufual way, to the day of ie 
month, for common ufe; but to the natural tangent of the 
declination, when great accuracy is required. 
Ue of the Univerfal Ring- 2. the line a ep 
’ 
