a. Rundway hill b. Oldbury D. Stonehenge.
The variation at Stonehenge is about 6 or 7 degrees, from the north eastward. I have in order to form our hypothesis, set down a scheme of the state of the variation in England, from the best observations I could meet with. Dr. Halley takes notice, that the variation at Paris is always 2 degrees and a half more easterly than with us. Orontius Finæus in 1550 observ’d it to be there, about 9 degrees, easterly, therefore to reduce it, I have stated it at 11 degrees 30. and from thence continued it, to the present time, as in the ensuing table.
| Anno Dom. | Observation. | Variation. deg. min. | |
|---|---|---|---|
1550 | By Finæus | 11 30 | east. |
1580 | Mr. Burroughs | 11 15 | east. |
1600 | 8 0 | east. | |
1622 | Mr. Gunter | 6 0 | east. |
1634 | Mr. Gellibrand | 4 5 | east. |
1642 | 3 5 | east. | |
1657 | Mr. Bond | 0 0 | |
1665 | Mr. Bond | 1 22 | west. |
1666 | Capt. Sturmy | 1 27 | west. |
1667 | Capt. Sturmy | 1 33 | west. |
1672 | Dr. Halley | 2 30 | west. |
1683 | 4 30 | west. | |
1685 | 5 5 | west. | |
1692 | 6 0 | west. | |
1723 | 11 0 | west. | |
1733 | 12 0 | west. | |
1740 | 15 45 | west. | |
By this table it appears, that in the space of 180 years, the variation of the magnetic needle in England, has shifted from 11 degrees and a half eastward, to 11 degrees and a half westward. In 90 years the medium of those extremes, which was 1657, there was no variation at all; the needle pointing due north and south. But alas our observations extend no farther. We know not the bound of the variation, on either hand: nor the quantity of its motion, when thereabouts. Mr. Geo. Graham thinks it is now near the western bound. It is very slow, in all probability, when upon the return, and as it were, stationary: like the sun’s motion at the tropics, when it is returning. So that the nice determination of its circle, and of its motion, is reserved for remote posterity. Dr. Halley conjectures, that the whole period of variation, is perform’d in about 700 years. Upon this supposition, in gross, we may thus found our conjecture, of the time of building of Stonehenge.
By what we can find, the variation is about 9 minutes in a year, or a degree and a half in 10 years, at this part of its circle. Now I observ’d at Stonehenge, that the eastern wing of the avenue, the cursus and other parts belonging to the temple, abated somewhat in their variation, eastward, being somewhat less than that of the temple itself. It is highly reasonable to believe, that the great work of Stonehenge could not take less than half a score years in building: and that those other works were made in succeeding years, not long after it was finished. From hence I gather, which way the magnetic variation was moving, at the time of founding Stonehenge, viz. from east toward no variation and so to west. This must be the foundation of our calculus.
Therefore at the time of the founding of Stonehenge, the variation was about the same quantity and place, as about A. D. 1620. in our preceding table. Supposing with Dr. Halley, the revolution of this variation be about 700 years, three intire revolutions thereof, bring us to about the year of the city of Rome 280. which is about 460 years before our Saviour’s time: 420 years before Cæsar invaded Britain. About 100 years before our Saviour’s birth, Divitiacus made the Wansdike north of Stonehenge, and drove the possessors of this fine country of the Wiltshire downs, northwards. So that the Druids enjoyed their magnificent work of Stonehenge, but about 360 years. And the very great number of barrows about it, requires, that we should not much shorten the time. Sir Isaac Newton in his Chronology, reckons 19 years for a medium of a king’s reign. So that in that space, there were about 19 kings, in this country. And there seems to be about that number of royal barrows (in my way of conjecturing) about the place.
I observe, this time we have assign’d for the building of Stonehenge, is not long after Cambyses’s invasion of Egypt. When he committed such horrid outrages there, and made such dismal havock, with the priests and inhabitants in general, that they fled the country to all parts of the world. Some went as far as the East Indies, and there taught many of the antient Egyptian customs; as is taken notice of by the learned. It is not to be doubted that some of them fled as far westward, into the island of Britain, and introduced some of their learning, arts and religion, among the Druids; and perhaps had a hand in this very work of Stonehenge: the only one that I know of, where the stones are chizel’d. All other works of theirs, are of rude stones, untouch’d of tool, exactly after the patriarchal and Jewish mode: therefore older.
This was at a time, when the Phœnician trade was at height, the readier a conveyance to Britain: it was before the second temple at Jerusalem was built: before the Grecians had any history.
Directions to the binder.