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.

Another Observation between London and Amsterdam, comparing it with Antwerp, being in the same Meridian of Amster∣dam. See Mr. Bonds Tables of Longi∣tude 4. d. 37 m. Eastward of the Meridian of London.

AMsterdam Latitude 52 d. 40 m. the Magnetick Latitude 74 d. 22 m. and in the Caroline Table the Magnetick Co∣latitude is 29 d. 16 m. and the distance of the Magnetick Pole, from the Pole of the Earth 8 d. 30 m. to find the Angle of the Pole of the Earth.

Here place the tenth Figure.

L S, the Co-latitude of Amsterdam, and N L, the Magnetick Colatitude, and S N is the distance of the Magnetick Pole, from the Pole of the Earth.

Now suppose I was at Amsterdam, and should observe and find it in the Latitude

[illustration] geometrical diagram

Fig: 10

of 52 d. 40 m. and should find the Incli∣nation or Magnetick Latitude 74 d. 22 m. and in the Caroline Table, the Magne∣tick Co-latitude to be 29 d. 16 m. And the Magnetick Pole distant from the Pole of the Earth 8 d. 30 m. So that by the fol∣lowing Work, I find the Angle of the Pole of the Earth to be 16 d. 30 m. then we are to substract 6 d. 00 m. as in the case of Ballasore, that the Magnetick Meridian (as Mr. Bond saith) is gone to the Eastward, and there remains 10 d. 30 m. for the dif∣ference of Longitude betwen London and Amsterdam: Whereas in Mr. Bonds Ta∣bles of Longitude he makes but 4 d. 37 m. Longitude Eastward of the Meridian of London, which being substracted out of 10 d. 30 d. there remains 5 d. 53 m. over and above the difference of Longitude be∣tween London and Amsterdam: So that the inclination of the Inclinatory Needle, with his Co-latitude, is not in proportion to the Meridian of London, or any certain Meridian of the Earth.

	d.	m.
L N,	29	16
S N, the residuum Sine	08	30	083029
S L, the residuum Sine	37	20	021720
The Sum of the sides	75	06
The Sine the half Sum	37	33	978494
The Side of opposite substract	29	16
The Sine of the difference	08	17	915856
The Sum			1999099
The Sine of the half Sum	81	45	999549½

The Complement of 81 d. 45 m. is 8. d. 15 m. the double thereof is 16 d. 30 m. for the Angle at the Pole of the Earth; and we are further to prove, that the inclina∣tion of the Inclinatory Needle with his Co-latitude at Amsterdam and Antwerp do alter the Angles at the Pole, although these two places are under one and the same Meridian of the Earth, when accord∣ing unto truth the Angles at the Pole of the Earth should be the same, when you are under one and the same Meridian of the Earth.

Antwerp Latitude 51 d. 37 m. N° the Magnetick Latitude, or Inclination 73 d. 48 m. N° the Magnetick Co-latitude in the Caroline Table 30 d. 09 m. the di∣stance of the Magnetick Pole, from the Pole of the Earth 08 d. 30 m. to find the Angle at the Pole of the Earth.

[illustration] geometrical diagram

Fig: 11.

	d.	m.
L N,	30	09
S N, the residuum Sine	38	23	020696
S L, the residuum Sine	08	30	083029
The Sum of the Sides	77	02
The Sine of the half Sum	38	31	979430
The Side opposite substract	30	09
The Sine of the difference	08	22	916288
The Sum			1999443
The Sine of the half Sum	83	31	999721½

The Complement of 83 d. 31 m. is 6 d. 29 m. the double thereof is 12 d. 58 m. the Angle at the Pole of the Earth. So having found the Angle at the Pole of the Earth, in the Meridian and Parallel of Antwerp to be 12 d. 58 m. I substract 12 d. 58 m. the Angle at the Pole of the Earth, from the Angle at the Pole of the Earth in the Meridian and Parallel of Amsterdam 16 d. 30 m. and there remains 3 d. 32 m. that the Angles at the Pole of of the Earth differ under one and the same Meridian of the Earth. For as all places under one and the same Parallel of the Earth, are in one and the same Latitude,

so have all places under one and the same Meridian of the Earth, the same Longitude from the Azores, or any other Meridian, from whence you will make the difference of Meridians to begin at.

So that if there was any truth in the Observation, from the Inclinatory Needle, it should give the Angles alike at the Pole; when you are under one and the same Me∣ridian of the Earth.

Portsmouth Latitude 51 d. 08 m. N°. the Magnetick Latitude, or inclination 72 d. 52 m. whose Complement in the Caro∣line Table is 31 d. 40 m. the distance of the Magnetick Poles, from the Poles of the Earth 8 d. 30 m. to find the Angle at the Pole of the Earth.

[illustration] geometrical diagram

Fig: 12.

	d.	m.
L N,	31	40
L S, the residuum Sine	38	52	020237
S N, the residuum Sine	08	30	083029
The Sum of the Sides	79	02
The Sine of the half Sum	39	31	980366
The Side opposite substracted	31	40
The Sine of the Difference	07	51	913538
The Sum			1997170
The Sine of the half Sum	75	27	998585

The Complement of 75 d. 27 m. is 14 d. 33 m. the double thereof is 29 d. 6 m.

the Angle at the Pole of the Earth, so the Angle at the Pole of the Earth is found to be 29 d. 6 m. So I add 4 d. 12 m. as in the Case of Cape Charles. Portsmouth be∣ing West of the Meridian of London, and it gives me 33 d. 18 m. the difference of Longitude between the Meridian of Lon∣don, and Portsmouth. And Mr. Bond makes but 01 d. 00 m. for the difference of their Meridians. See his Tables.

Lastly, we may observe from Mr. Bonds Observation taken in London by the Incli∣natory Needle, whether London be the Me∣ridian, from whence the Magnetical Lati∣tude or Inclination, with the Co-latitude in the Caroline Table, and the Co-latitude of London, with the distance of the Mag∣netick Pole, from the Pole of the Earth, will give London to be the Meridian, from whence the Magnetick Co-latitude, with the other proportions, shall give the An∣gle at the Pole of the Earth, to be 6 d. 00 m. that the Magnetick Pole is from the Meridian of London Eastwards, as Mr. Bonds faith in the case of Ballasore. But if the Angle appear to be more or less

than 6 d. then the Inclination of the Incli∣natory Needle, is not in proportion to the Meridian of London; so that London cannot be said to be the Meridian, from whence Longitude shall begin at.

London Latitude 51 d. 32 m. the Mag∣netick Latitude or Inclination 73 d. 47 m. the Magnetick Co-latitude in the Caroline Table 30 d. 11 m. the distance of the Magnetick Pole, from the Pole of the Earth 8 d. 30 m. to find the Angle at the Pole of the Earth. I. S N.

	d.	m.
N L,	30	11
S L, the residuum Sine of	38	28	020616
N S, the residuum Sine of	08	30	083029
The Sum of the Sides	77	09
The half Sum, the Sine	38	34½	979478
The Side opposite substract	30	11
The Sine of the difference	08	23	916374
The Sum			1999497
The Sine of the half Sum	83	51	999748½

[illustration] geometrical diagram

Fig. 13:

The Complement of 83 d. 51 m. is 6 d. 09 m. the double thereof is 12 d. 18 m. the Angle at the Pole of the Earth L S N.

Here place the thirteenth Figure.

So is L N, the Magnetick Co-latitude 30 d. 11 m. and L S is the Co-latitude of London 38 d. 28 m. and S N, is the Mag∣netick Pole distant from the Pole of the Earth 8 d. 30 m. so that the Angle at the Pole of the Earth L S N, is found to be 12 d. 18 m. in the Meridian and Parallel of London, then substract 60 d. 00 m. from 12 d. 18 m. as in the case of Ballasore. That Mr. Bond saith the Magnetick Pole is from the Meridian of London, and you have 6 d. 18 m. for the difference of Longitude in the Meridian of London; whereas Mr. Bond saith London has no Longitude: See his Tables. So that Mr. Bond must be under a very great mistake in making the Magnetick Inclination of

the Inclinatory Needle at London, to be in proportion, unto the Meridian of Lon∣don, from whence Longitude shall begin at. When according to his own Observa∣tion by the Inclinatory Needle in Lon∣don, with the Magnetical Colatitude in the Caroline Table, and the Co-latitude of London, and the distance of the Mag∣netick Pole, from the Pole of the Earth, London should have Longitude 6 d. 18 m. having given the Allowance Mr. Bond requires, as in the case of Balla∣sore.

The truth is the Inclination of the In∣clinatory Needle, is not in proportion unto the Meridian of London, or any cer∣tain Meridian of the Earth, whereby the difference of the Meridians may be known by the Inclination of the Inclina∣tory Needle.

To sum up all; Mr. Bond pretends to find, what the Magnetick Meridian is gone to the Eastward, as in the case of Balla∣sore, by saying let the Angle W P N be 6 d. 00 m. that the Magnetick Pole is from the Meridian of London. Whereas

the Angle W P N, according to the pro∣portions of the Sides and Angles, contained in the Angles P. B N, is 37 d. 59 m. and not 6 d. 00 m. that the Magnetick Pole is gone to the Eastward of the Meridian of London. And the Angle W P B is 87 d. 13 m. and not 119 d. 12 m. by Jour∣nal.

Likewise it is proved, that all places in one and the same Meridian of the Earth, do alter their Angles at the Pole, from the Observations of the Inclinatory Needle, when according to truth all places, under one and the same Meridian of the Earth, should make one and the same Angle at the Pole, otherwise the difference of Me∣ridians cannot be found.

Likewise it is proved from several places near unto the Meridian of London, and in the Meridian of London, that the Angles at the Pole of the Earth, is no way in pro∣portion unto the Meridian of London, or that London is the Meridian from whence Longitude shall take its beginning in pro∣portion to the Inclination of the Inclina∣tory Needle. So that the Inclination of the

In∣clinatory Needle is no way in proportion unto any certain Meridian of the Earth, from whence all Meridians should take their Distance.

For these Reasons the Longitude cannot be found by the Inclinato∣ry Needle.