Page:Philosophical Transactions

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set to its right measure, but that B. goes every day 7 sec. to slow, and C. every day 12. see. too fast. Some days after, suppose the 5th of May, desiring to know the Longitude of the place where you are at Sea, you observe the time of the day

	h.	min.	sec.
there to be	5	10
And you find the Watch A. to point at	2	6	0
But the Watch B. to point at	1	57	22
Going too slow by 7. sec. every day, which makes in 74. days, (viz.
From the 20th of Febr. to the 5th of May)	0	8	38
Which being added to its own time, gives the same
	h.	min.	sec.
with than of the Watch A. viz.	2	6	0
You find also the Watch C to point at	2	20	48
Going 12 sec. too fast every day, which makes in 74. days	0	14	48
Which being subducted from its owne time gives again	2	6	0
The time of day therefore by the Watches being	2	6	0
Adde thereunto the Æquation of the 5th of May	0	19	29
And so you have for the time of day at the place where the Watches were set	2	25	29
But, the time observ'd being	5	18	10
Exceeds this by	2	52	41
Wherefore the Meridian of the place, where you are May 5th, is more Easterly, than the places where the Watches were set, by	2	52	41
	deg.	m.	d.
Which being reduced to degrees, reckoning 15 deg. for an hour, comes to	43	10	15

'Tis true, that from the same reckoning it may be concluded, that you are 180. deg, more Easterly, which happens because the Hour-Index goes round in the space of 12. hours in the Watches; but the difference is so great, that one cannot be deceiv'd in it; else the Watch might be so made, that the Index shall goe round but once in 24 hours.

7.

To find the time of the Day at Sea.

Since that for finding the Longitude, the Time of the day

at

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