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| d. | m. | ||
| LN, | 72 | 33 | |
| NS, the residuum Sine | 08 | 30 | 083029 |
| SL, the residuum Sine | 67 | 30 | 003438 |
| The Sum of the sides | 148 | 33 | |
| The half Sum | 74 | 16½ | |
| The Sine of the first difference | 65 | 56 | 995993 |
| The Sine of the second difference | 6 | 46 | 907124 |
| The Sum | 1989584 | ||
| The half Sum | 994792 |
994792 the sine thereof is 62 d. 30 m. the double thereof is 125 d. 00 m. the An∣gle at the Pole of the Earth N S L, which should be the Difference of Longitude: But since Mr. Bond makes London the first Meridian, from whence Longitude shall take its beginning, as in the Question be∣fore, Ballasore should have Longitude 125 d. 00 m. East of the Meridian of London; let the Table of Longitude say what it will, for the Table of Longitudes is no other than the difference of Meridians by Jour∣nal: But if I find the difference of Longi∣tude by the Magnetick Co-latitude, and the distance of the Magnetick Pole, and the Co-latitude of the place, it should correct what has been laid down by Jour∣nal; for I do not take what has been laid down by Journal to be true, in regard there is no certain Observation to lead us to it: For if London be not the Meridian, from whence the Magnetick Co-latitude takes its beginning towards the Magnetick Poles; then the distance of the Magnetick Meridian from the Meridian of London, cannot give the difference of Meridians.
Mr. Bonds way to prove what the Mag∣netick Meridian is gone to the Eastwards, is thus: First, he knows his Magnetick Co-latitude at Ballasore, and the Co-la∣titude of the place, and the distance of the Magnetick Pole; and so finds the di∣stance of the Magnetick Meridian, from the Meridian of London 125 d. 00 m. so then finding 125 d. 00 m. doth not an∣swer the Longitude by Journal; he pro∣ceeds to find what the Magnetick Meridi∣an is gone to the Eastwards: thus, he gives the Co-latitude, and the distance of the Magnetick Pole, and the Longitude by Journal 119 d. 12 m. and to this he adds 6 d. which makes 125 d. 12 m. the distance of the Magnetick Meridian, to find the Magnetick Co-latitude: This is but turning the Question.
So that you must know your Longitude by Journal 119 d. 12 m. before you can find what the Magnetick Meridian is gone to the Eastwards.
Mr. Bonds way is thus: Substract 119 d. 12 m. the Longitude by Journal, from 125 d. 12 m. the distance of the Magne∣tick
Meridian, from the Meridian of Lon∣don, and you have 6 d. 00 m. that the Magnetick Meridian is gone to the East∣wards: So by this Mr. Bond produced the Longitude by Journal, to correct the distance of the Magnetick Meridian, from the Meridian of London.
Mr. Bond must know that Longitude by Journal in all the World is laid down by Judgement; and then how rare is it for any one man, who hath been at any one Port in the World, somewhat remote, that hath found it in the very same Meridian, in regard of the many accidents that at∣tend the Practical part of the Mathematicks at Sea?
And then how is it possible to know the Longitude I am in, by the distance of the Magnetick Meridian? If I must first know the Longitude by Journal, which I cannot prove to be certain, and so correct the Observation by it, so that by this way of practice, the Inclinatory Needle is of no use; for the Magnetick Latitude, with the other proportions before, should give the Longitude without the help
of a Journal to correct his Observa∣tion.
The next thing we are further to consi∣der of is, how Mr. Bond finds what the Magnetick Meridian is gone to the East∣wards of Ballasore.
We may observe from Mr. Bonds own Sphere and Words; let the Angle W P N, be 6 d. 00 m. but this Angle W P N is not to be passed by, with a let it be so; but it must be found in proportion to the several sides, and Angles given in the Sphere. First I shall give the Co-latitude of Ballasore 67 d. 30 m. P B, and the Angle B P N 125 d. 12 m. and the Mag∣netick Co-latitude 72 d. 33 m. to find the Angle P N B.