Thomas Jefferson Papers

To Thomas Jefferson from John Ledyard, 7 July 1786

From John Ledyard

St Germain en Laye July 7th 86


It is with great defference that I write you a letter of this kind; and yet was you a king or the minister of a king I should not have wrote it had the access been the same.

Attraction appears to be the first natural cause of motion in all bodies. I suppose the whole system of modern natural philosophy rests upon it whenever it respects motion. This being the case that particular motion which respects magnetism becomes a part of this universal cause. As motion is as universal as existance so it is as various as universal. To assign reasons therefore for the motion of a part and not the whole is partial.

If the Sun is the center of attractive motion why is it not also the center of that motion we observe in the magnetic needle. If it is, it immediately follows that as the central cause, it is the greatest cause. If it is the greatest cause in what manner as such does it operate on the magnetic needle to produce that motion which we call the variation of the needle.

If the Sun has an effect upon the motion of the magnetic needle, those motions can be made a matter of calculation and reduceable to rule.

I only offer one reason why I can suppose the Sun to operate on the motion of the magnetic needle, which is that the greatest variation of the needle seems to be when at the greatest distance from the Sun and that variation an inclination to the Sun.

This Idea of the sun having the particular influence just mentioned struck me as new, rational and worthy communicating to you. If it should appear so to you I shall be exceedingly honoured.

The letter left for me at your address was from a Gentleman at Edinburgh concerning my affair with the Marquis of Buckingham from whom I expect some intelligence in about a week.

In returning from Paris as I was walking on the skirt of a wood by the side of the high road about ten o clock I heard a horse stumble and fall and a Person give one groan. I sprang into the road to see what was the matter and found a Man down under his horse and both so entangled together that neither could rise. In making a suden strong effort to disengage the Man I so much strained my loins that I have been ever since Confined to my room—but am better. The Man was much hurt.

I have the honor to be Sr. Your much obliged most respectfull & most humble servt.,

J Ledyard

RC (DLC); endorsed. Noted in SJL as received 7 July 1786.

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