( 641 ) *
care to Observe that Time as precisely as is possible. For every Minute ofTime, that you misreckon, makes 4 Degree in Longitudc , which amounts,
Tiear the JEquator, to above 15 Englijh Miles, but less elsewherc. Wherc-fore to find the Time os the Day with certainty, the best: way is to Observethe Suns Attitüde when it is in the Fast or West, ( the nearer the bettet : )for being there, its Altitudc Changes in a short Time more senhbly than bc-fore or aster ; and thus from the Height of the Pole and the Declination otthe Sun the Hour may be Calculated.
7. At the EJßng and Sctting of the Sun, when it is half above the Iloriqon, t ,,ß cr 1
mark the Tinte of the Day, which the iVatches then shew; and though yehave in the mean time sailed on, it is not Considerable. Then Reckon by theM'atchcs, what Time is elapfed between them, and Add the half thcrcof to•the Time of the RJßng, and you (hall have the Time by the IVatches, wh.cnthe Sun was at South ; to which is to bc added the JEquation of the prefentDay by the Table. And it this together makes 12. Hours, then was theShipat Noon under the säme Meridian, where the IVatches were Set with the Sun.
But if the Summ be more than 12., then was the at Noon under a morehl'cstcrly Meridian ; and if less, then under a more Eaflerly ; and that by asmany Times ry Deg. as that Summ Excecds or Comcs stiort Hours of iz,as the Calculation thereof hath been already deliver’d.
Suppose, e. g. that the IVatches A and B, as before, were set with the Sunat the Place whence you Parted, the 20 of Fchruary ; and the Indexes set to
-the Hour, Min. and See. shewed by the Sun, abating the AEquation of thatday, i'i'y. 1! 10" ; the H'atch A being Reduced to the Right Measure, andB going too slow by y ,r a day. Afterwayds on the zz d of May, desiring toknow the Longitudo of the Place to which you are come, you Observe in theMorning the Sun half above the Horizon, when the fVatch points at—-ZhAnd in the Evcning, the Sun being half under the I-Iori^on,
when the sam e H'atch points at- - 3
To find the Time Elapfed between them, Subducting the Time
of the Rjfing --
F rom- ——- — -
Adding thereunto the Time os the
There Remains-Setti ng ■ ■ -
You have for the time Elapfed between the Observations-
Whereof the Half-
Being Added to the Time of Eyfing
iz
-9
-3
-12
-6■ 1
You have the Time by the fVatch A, when © was in the Soutl -8
And aster the säme mannet you are to seek the Time by the
l-Vatch B, when the Sun was in the South ; which Let be-8
But this iVatch going q" a day too slow, it is Retarded in 91 days
(from the zc th of Febr. to the zz « 1 of May) --0
Which therefore Added to the said Time gives * 1 -8
That is the säme Time given by the ITatch A. Now Addingto this Time of the IVatches, the /Equation of the zz<l of May — o
You have . . >- — —... ... ..... > 9
Vol. I. N n n n
3 c'
IO 1 '
8
40
30
10
0
0
29
5 o
8
40
38
30
W
ts
3 °
10
49
zy
38
48
10
37
49
2.)
18
10
7
35
Which
\
N n n h