Quincy January 12. 1803.
I recd last night yours of the 6th.—I read the Account of the Small Globe rolling in a little Pool of Mercury: but have heard no more of it.
The Powers of the Magnet are indeed among the Arcana of Nature: and what is not? Nature itself is all arcanum: and I believe will remain So. It was not intended that Men with their Strong Passions, and weak Principles, Should know much. Without a more decisive and magisterial moral discernment much knowledge would make them too enterprising and impudent. The human Species will always be, only of yesterday and know nothing.
A Mr Churchman has taken great pains to form a Chart of the Variations of the magnetic Needle, over the whole Globe for the purpose of ascertaining the Longitude; and I believe many navigators have used them at Sea. Some of the Scientific People in France and England, have expressed this approbation of the Idea and encouraged its pursuit. But if Mr Sewalls Observations at Cambridge are correct the variations change So often, in every day, that there is room to doubt of the Utility of this thought.—Yet upon the whole, I think in general, that it may be of some Use: and that very often, in the hands of a Skillfull and attentive Navigator. Churchman is a Native of America.
Another of our Countrymen, Jonathan Williams, born in Boston, has projected uses for the Thermometer in Navigation. If you have not Seen it, you will receive Some Amusement from it. Pray return it to me by the Post, when you have perused it to your Satisfaction; because it is a present and the only copy, I have. The discovery of Banks and Soundings by Mercury in a glass, is not an obvious thought, but it may be well founded.
The Pitchings and rollings of the Ship have no effect on the magnetic needle, at Sea. The Swiftness and Slowness of her motions have no more.—What then may not a little wooden Globe inclosing a Loadstone and Wallowing in Mercury, Shew the Variation of the Needle? But I Suspect that this machinery, was used in connection with Churchmans Variation Chart. If there is any thing Solid in the Story, We Shall hear more of it: probably however in some Patent for the exclusive Sale of the machine.
There was a Fairy, who carried on, a manufactory, with his little Mill, in Hemmenways brain, in his Sleep when he was at College, and furnished him with a quantity of Verses, which he could repeat, in the morning from his dream, which Seemed very much like the Inspiration of the Muses. Most Poets would have said, with Eve or Adam, when they Saw themselves in the Water "This, fair Creature, is thyself."—But Dr Hemmenway has perused Studies more Satisfactory to himself, and useful to others.
An occasional correspondence, will be very agreable to me.—I am nevetheless as busy as ever I was.—My private affairs, neglected for eight and twenty years, now call for my constant attention. I Shall never be So busy as not to receive pleasure from your Letters.—
Yours with great esteem
MHi: Adams Family Papers, Letterbooks.