When I had read your Favour of May the 14th.6 I resolved to read and consider more carefully Sir Isaac Newton’s Optics, which I have not look’d at these many Years. I delay’d answering, till I should have an Opportunity of doing this; but one thing or other has hitherto hindred. In the Winter I may possibly have more Leisure.

In the mean time I would just mention, That the Interposition of a Hill between a Bell and the Ear, does interrupt great Part of the Sound, tho’ not all; And we cannot be certain that an opaque Body plac’d between the Eye and a luminous Body intercepts all the Light, since, as you observe, it does not follow that where we see no Light there is therefore none existing. What you say of the Separation of the distinct Parts of Light, which once separated remain always the same, has more Weight with me, and indeed seems conclusive; at least I see at present nothing to object.

I congratulate you on the Prospect you have, of passing the Remainder of Life in philosophical Retirement. I wish for the same, but it seems too distant. I might then more punctually perform my Part in the Correspondence you honour me with; than which I have none more instructive or agreable.

Send me, if you please, the Translation of your Piece into High Dutch.7 I understand a little of the German Language, and will peruse and return it. At present, I cannot guess the Meaning of the Passage you mention. Unless perhaps, as your 20th Section speaks of “a Power that neither resists nor moves, and exerts no kind of Action of itself, without the Concurrence of some other Power; so that in the Absence of other Powers it must be in perfect Inaction, &c.” it may be some kind of Dutch Wit, and intended to joke that Quietism which in Germany is supposed to be very prevalent in Pensilvania, many of their Quietists having removed hither.

I see by Cave’s May Magazine they have translated my Electrical Papers into French, and printed them in Paris.8 I hope our Friend Collinson will procure and send me a Copy of the Translation. Such Things should be done by Men skilled in the Subject as well as in the Language, otherwise great Mistakes are easily made, and the clearest Matters rendred obscure and unintelligible.

I am sorry you could not see Mr. Kinnersley’s Lectures; they would have pleas’d you. I send you Mr. Wilson’s Book,9 which I just receiv’d from London, and think it contains the best Directions for the Use of the Machine that are extant. When you have done with it, please to return it to Dear Sir Your most humble Servant