Front Page Titles (by Subject) XCI: TO CADWALLADER COLDEN - The Works of Benjamin Franklin, Vol. II Letters and Misc. Writings 1735-1753
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XCI: TO CADWALLADER COLDEN - Benjamin Franklin, The Works of Benjamin Franklin, Vol. II Letters and Misc. Writings 1735-1753 
The Works of Benjamin Franklin, including the Private as well as the Official and Scientific Correspondence, together with the Unmutilated and Correct Version of the Autobiography, compiled and edited by John Bigelow (New York: G.P. Putnam’s Sons, 1904). The Federal Edition in 12 volumes. Vol. II (Letters and Misc. Writings 1735-1753).
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TO CADWALLADER COLDEN
Philadelphia, 14 September, 1752.
When I had read your favor of May the 20th, I resolved to read and consider more carefully Sir Isaac Newton’s Optics, which I have not looked at these many years. I delayed answering till I should have an opportunity of doing this, but one thing or other has hitherto hindered. 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 a great part of the sound, though not all; and we cannot be certain that an opaque body placed between the eye and a luminous object 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 honor me with; than which I have none more instructive or agreeable.
Send me, if you please, the translation of your piece into High Dutch. 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 twentieth 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 a 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 Pennsylvania, many of their Quietists1 having removed hither.
I see by Cave’s Magazine for May that they have translated my electrical papers into French, and printed them in Paris. 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 rendered obscure and unintelligible.