Tractatus de Globis et Eorum Usu. a Treatise Descriptive of the Globes Constructed by Emery Molyneux by Markham Clements R.;

Author:Markham, Clements R.;
Language: eng
Format: epub
Publisher: Taylor & Francis Group

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I. The difference of Longitude and Latitude of two places beingknowne, how to find out the Rumbe and Distance of the same.

Turne about the Globe, until that some Rumbe or other do crosse the Meridian, at the latitude of the place whence you set forth. Then again turne about either toward the East or West, as the matter shall require, untill that an equall number of degrees in the Equator to the difference of longitude of the two places do passe the Meridian. Then afterward looke whether or no the aforesaid Rumbe doe crosse the Meridian at the latitude of the place where you are, for if it does so you may then conclude that it is the Rumbe you have gone by; but if otherwise, you must take another, and try it in like manner, till you light upon one that will do it.

As for example. Serra Leona is a Promontory of Africke, having in longitude 15 gr. 20 min., and in Northerne Latitude 7 gr. 30 m. Suppose that we are to saile to the Isle of Saint Helen, which hath in longitude 24 gr. 30 m. and in Southerne latitude 15 gr. 30 m., I now demand what Rumbe we are to saile by; and this we find in this manner. I first apply to the Meridian the 356 gr. 40 m. of longitude, and withall observe what Rumbe the Meridian doth crosse at the latitude Northerne of 7 gr. 30 m. (which is the latitude of the place, whence we are to set forth): and I finde it to be the North norwest, and South southeast Rumbe. Then I turne about the Globe toward the West, (because Saint Helens is more Eastward than Serra Leona untill that 9 gr. 10 m. in the Æquator, which is the difference of longitude betwixt these two places) do crosse the Meridian. And in this position of the Globe, I finde that the same Rumbe is crossed by the Meridian in the Southerne latitude of 15 gr. 30 m., which is the latitude of Saint Helens Isle. Therefore I conclude that this is the Rumbe that we are to go by, from Serra Leona to Saint Helens. And in this manner you may find the Rumbe betwixt any two places either expressed in the Globe, or otherwise; so that the difference of longitude and latitude be but knowne.

The….

13. 18 Long, 8. 30 Laot.

* 5. 44.

15. 55. N.

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