A regiment for the sea conteyning most profitable rules, mathematical experiences, and perfect knovvledge of nauigation, for all coastes and countreys: most needefull and necessarie for all seafaring men and trauellers, as pilotes, mariners, marchants. [et] c. Exactly deuised and made by VVilliam Bourne.

¶The second Chapter or rule treateth of the Golden number or Prime, shewing the Epacte, and by the Epacte to knowe the Age of the Moone.

IT is necessary and conuenient for the Seafaring men, to knowe the Prime or Golden number: for by the Golden number is knowne the Epacte, and the Epacte sheweth the age of the Moone or chaunge day, within .12. houres vnder or ouer: and by the age of the Moone, you may know at what a clocke it doth flowe in any place that you doe knowe what Moone doth make a full Sea: therefore it is méete too know the Epacte, and that is knowne by the Pryme, or Golden number. The cause why it was called the Golden number, was bycause it was sent out of Egypte in letters of golde, too the Romaines or Citie of Rome. The cause why that it is called the Pryme, was for that it was the first order that the Moones course was known by, and it is thus knowne. Adde one to the yeare of our Lord that you would knowe the Gol∣den number or Pryme of, then deuide the number by .19. the remainer is the Pryme: and multiply that by .11. and looke what the number commeth vnto, deuide that by .30. the re∣mayner is the Epact. Then when you haue once the Epact, adde .11. to your Epact for euery yere more, and looke what that commeth to, that is your Epact: and if it do passe .30. put that away, and keepe the remainer for your Epact. And thus this rule will serue for euer, sauing when the Pryme begin∣neth at one, for then the Epacte is .11. and then doe (as afore∣sayde) as you may perceyue by this table héere following.

¶The Table of Pryme and E∣pacte for .19. yeares, and vvhen those .19. yeares be ended, then beginne againe, and so it will serue for euer. &c.

The yere of the Lorde.	Pryme.	Epact.
1574	17	7
1575	18	18
1576	19	29
1577	1	11
1578	2	22
1579	3	3
1580	4	14
1581	5	25
1582	6	6
1583	7	17
1584	8	28
1585	9	9
1586	10	20
1587	11	1
1588	12	12
1589	13	23
1590	14	4
1591	15	15
1592	16	26

THe Prime or Golden number, is the time of .19. yeares, in the which time the Moone maketh all hir chaunges or coniunctions with the Sunne, and when all these .19. yeares be expired, then she beginneth againe: as for example. This yeare being the yeare of our Lord .1574. she chaunged the .22. day of March, and euery yere doth alter .11. days of hir change till the yere .1593. and then she chaungeth the sayd .22. daye of March againe, as I shewed you before. The Epacte is the putting to .11. for euery yeare. Nowe furthermore to knowe the age of the Moone, do thus: take the number of the Epact for your yere (beginning at March alwayes) and recken how many monthes it is from March, (counting March for one)

then recken howe many dayes of the moneth it is in whiche you would knowe the age of the Moone: Then put all your numbers togither, (that is to say, your Epacte, your moneth from March, and euery day of the moneth,) then looke howe many it amounteth vnto, that is the age of the Moone, but if it passe .30. throwe all the .30. away, and kéepe that that will not be .30. for when the age of the Moone is iust .30. then is it the chaunge daye: and if it be the fiftéenth daye of the age of the Moone, then the Moone is at the full. When the age is betwéene seuen dayes and eight, then is the first quar∣ter. And if it be .xxij. dayes olde, then the Moone is at the laste quarter: as for example, this yeare .1574. I looke and finde the Epacte .7. for the yeare, nowe I woulde knowe the age of the Moone, the .13. daye of Iune. Nowe I recken how many monthes it is from March, reckning March for one, and I finde it is foure monethes, then I take and adde all these togyther, that is to say, seuen for the Epacte, and foure for the monethes (that is to say, March, Aprill, May, Iune) and then .13. for the dayes of the moneth, and all commeth to .24. So that you may conclude that the Moone is .24. days olde, and was at the last quarter two dayes before.

Notes

• The cause why that it was called the Pryme or Golden number.
• To knowe howe many the Epact is.
• The pryme is the time of .19. yeres
• To knowe the age of the Moone by the num∣ber of the Epact.