It hath been remarked that the magnetick Poles must be from the direction of the magnetick Needle some where about the Poles of the Earth, to find the situation thereof also to ascertain if there was any particular shot in the Earth to which the Needle uniformly pointed, when uninfluenced by partial causes such as Iron Ores, or any magnetick Bodies interposed or adjacent (thrusts?); and likewise to ascertain the Laws of motion by which it is governed, this was a favourite Scheme of the celebrated Doctor Halley but notwithstanding the many accurate observations made by him at the public charge and for want of their being universal and for want of laying them down on a Globe with a flexible ruler he seems to have fallen something short of finding the exact situation of the magnetick Poles, and thereby lost the satisfaction which modern times afford of finding the longiture at Sea, in a simple easy and certain way, without any additional Instruments to those in common use.

Having bestowed some time in the examination of various observations made by the most able navigators particularly those made on Captain Cooks last voyage to whom I hold myself under many obligations. I have compared with a System which to me had appeared the only reasonable one that the circumstances observed to attend the variations would warrant. I have ventured to make the following conclusions which I am encouraged x tho with the greatest diffidence to lay before you in hopes they may prove of some utility and are as follows 1st. That the Magnetick Needle hath a direction to two points at certain distances from each Pole of the Earth. 2nd. That these points to which it hath a direction are called the magnetick Poles 3rd. That one of these Poles is formd by laying down many observations in the Northern Hemisphere to be at a certain distance from the North Pole of the Earth, which for distinction may be called the North Magnetick Pole. 4th. That in the Southern Hemisphere the South point of the Needle hath a direction to a spot or point at a certain distance from the South Pole of the Earth altho not diametrically opposite to the other, which may be called the South Magnetick Pole 5th That a Line crossing the Meridians of the Earth at equal distant between the two magnetick Poles we call the Magnetick Equator 6th That Straight Lines drawn by a flexible ruler from the magnetick Equator to the North and South Magnetick Poles are or may be called Magnetick Meridians. 7th. That the Globe on which they are laid may be called the Variation Globes 8th. That when the Magnetick Pole is on the meridian of any place whether above or below the Pole of the Earth (except as hereafter excepted) there is novariation in that place or that the Line of no variation coincides with the meridian 9th That the greater the distance from the Line of no variation; the greater is the Variation of the Magnetick Needle. 10 That there are four several kinds of variations 11th That the Engle between the Meridian of the Earth and the Magnetic Meridian is called the Variation of the Magnetick needle or variation of the Compass. 12th That the space which the Magnetic Pole moves in a Year or any given time at the same rate thereby making an Universal change or alteration in the Angle between the Magnetick Meridian and those of the Earth is called the annual Variation. 13th. That the small alteration of the pointing of the Magnetick Needle in different times of the day found by making the Instrument first in one position; is called the diurnal variation 14th. That the fourth kind of variation is a small deviation which the needle makes from the true magnetick Meridian, which happens at certain times at certain places on the Globe, at certain distances from the Magnetick Equator, where the Needle appears to point not directly to either of the magnetic Poles, but a mein between the two, but the nigher we approach either of the Magnetic Poles the less is the Variation of the Needle from the true Magnetic Meridian, and at length it appears insensible which we suppose to be occasioned by the two Magnetick Poles being at different distances from the Poles of the Earth and of consequence not diametrically opposite to each other 15th. Haveing all these observations of the Variation laid down upon A Globe which have been made with a sufficient degree of accuracy they will intersect each other in the Magnetick Poles, and by the observations of the Variation of the compass at the Royal Societys House in London, by calculation we are enabled to fix the distance between the North Magnetick Pole and the Pole of the Earth with a degree of accuracy 16th. From whence there is reason to suppose that the place of concurrence of the Magnetick meridians are at certain times in the same places appearing to be moveable in a circle nearly equidistant from the North and South Poles of the Earth.

That these Poles have an uniform motion and perform revolutions in given times from West to East the Northern in about   Years the Southern one for want of sufficient observations for so long a time past, we cannot so accurately determine.

Hence by knowing the distance between the Poles of the Earth and Magnetick Poles we are enabled to form a set of rules for ascertaining the Longitude at Sea from an observation of the Latitude and Variation of the Compass, and vice versa from the Latitude and Longitude given to shew the Variation heretofore or to come.