The longitude not found, or, An answer to a treatise written by Henry Bond, Senior, shewing a way to find the longitude by the magnetical inclinatory needle wherein is proved that the longitude is not, nor cannot be found by the magnetical inclinatory needle / by Peter Blackborrow, Gent.

THE PREFACE.

WHen I first met with Mr. Bond's Book, I was in good hope to have found the Work answerable to the Ti∣tle, the Author being reputed (not without de∣sert) skilful in Mathematical Learning: But when I found his Doctrine want De∣monstration, (an Excellency in the Mathe∣maticks above all other Sciences Inseparable, for what is Truth therein, may always be demonstrated to be so) I began to doubt that (instead of so useful a Discourse, as he pre∣tended to) he might not only be deceived himself, but might also mislead others in the search thereof.

This made me take upon me the Exami∣nation

of the Work, which I profess to have done with that care and integrity, which is necessary in such an Ʋndertaking: And I do unfeignedly declare, that I am sorry (for the Authors sake) to find his Propositions unsound, and his Examples incertain. But let Truth be always True, the whole Founda∣tion of his Work is only an Airy Imaginati∣on, and the Superstructure is made up of false Suppositions, and impossible Conclusions.

A short Prospect whereof I have inserted here (for instant sake) from his own Exam∣ples, leaving the fuller Demonstration there∣of to the ensuing Treatise.

First, the Author pretends, that the Mag∣netical Poles are distant from the Poles of the Earth, by an Oblique Angle; which Angle is proved to be a false supposition, and cannot be demonstrated upon the Globe. But if it should be granted him, that the Magnetick Pole were 8 d. 30 m. from the Pole of the Earth, in the year 1580. then it is proved that the Magnetical Poles are found to be so by the Variation that was at Vaygats, and London in the year 1580. So that the Mag∣netical Pole must be as various as the Varia∣tion;

in regard it cannot be found without it. Then the Caroline Table being Calculated by the distance of the Magnetical Poles, from the Poles of the Earth, is useless, in regard it is proved, that the Magnetick Pole is as various as the Variation.

And in the next place the Author pretends to find, that the Magnetical Pole of the Me∣ridian of London, is gone to the Eastwards from his Observation made at Ballasore; and here he produceth the Longitude by the Practical Part of the Mathematicks at Sea by Journal, to correct his Observations by the Inclinatory Needle. Mr. Bond begs the Question: Let the Angle W P N be 6 d. 00 m. that the Magnetical Meridian is gone to the Eastward, when it is proved to be 37 d. 59 m.

So likewise in the case of Cape Charles, and in the Straits of Magellan (and all places Westwards of the Meridian of the Lizard.) Mr. Bond begs the Question: Let S K P F represent the Meridian of the Lizard, which is 4 d. 12 m. to the Eastwards of the Mag∣netical Colure, as appears by his Demonstra∣tion, which Angle at Cape Charles, is found

to be above 50 d. and not 4 d. 12 m. and the Angle at the Straits at Magellan, is found to be above 38 d. 00 m. and not 4 d. 12 m. I have omited to put down Mr. Bond's De∣monstration to prove his Errors, in regard it would produce many Cuts: but those that would be better satisfied, may take the same Method I used in the Case of Ballasore, where Mr. Bond says let the Angle W P N be 6 d. that the Magnetick Pole is gone from the Meridian of London; when the Angle is proved to be 37 d. 59 m.

And farther it is proved, where two places differing in Latitude, under one and the same Meridian of the Earth, that the Angle at the Pole doth alter, whereas all places, under one and the same Meridian, have one and the same Longitude.

And whereas Mr. Bond has altered the Meridian of the Azores, and has made Lon∣don the Meridian, from whence Longitude shall begin at: Longitude 00 d. 00 m. It is proved from Mr. Bond's own Observation, that London should have Longitude. Then the Magnetical Inclinatory Needle is not in proportion to the Meridian of London, or

any certain Meridian of the Earth.

And last of all, the Author supposeth the Magnetical Poles in the Air, some small distance from the Earth, which (as he says) may be a great reason of the Motion of the Earth, and to that end, he has drawn his Spheres accordingly: But I have proved that Mr. Bond's Question between Ballasore and London, is to be demonstrated from the Globe of the Earth: So that all Questions that have the like Matter, have the like Demon∣stration: then why should we fancy the Mag∣netick Poles in the Air?

And farther I have added a small Trea∣tise, proving by several Observations, and Demonstrations, that the Earth is the Center of the Starry Heaven; and that it has no Motion upon its Axis; and for any one to pretend the Earth to have a Motion from West to East, it is only imagination; for there is no Observation to prove it. I know there are many men of a contrary opinion; but I would have such men to produce Obser∣vation and Demonstration to prove the con∣trary.

I shall say no more in this place, but refer

to the Work it self; where if I have also erred, I shall gladly receive admonition from the Learned; but if I have not, I hope my Na∣tive Country will not take it unkindly, that I have discovered a dangerous Error, which (if followed, and relyed upon) would have been of fatal Consequence.

Peter Blackborrow.