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POSTSCRIPT
Sent by the same Noble Author from the same place,
December 6. 1667.
My condition in point of health being not much improved since I writ to you in October last, when I shall have added, that I have not these five or six weeks been able to procure any Shining Wood (except one single piece, which, though large, was so ill condition'd, that it afforded me but one Trial) you will not, I hope, expect, that I should add much to the Experiments I formerly sent you, about the Relation 'twixt Light and Air. But however, since the Subject is new and noble, and since your curiosity about other matters has been so welcome and useful to the Virtuosi, I shall not decline even on this occasion to comply with it, and the rather, because I half promised you some Additionals a good while since, and because too, that though, what I shall acquaint you with, may seem to be but a Confirmation of two or three of the former Experiments; yet, besides that 'tis of them which most needed a Confirmation, these Trials will also afford some Circumstances that will not, I think, be unwelcom.
Experiment XI.
To examine then the Conjecture mentioned in the last Experiment, That the durableness of the Light in the Shining Fish, in spight of the withdrawing the Air, might proceed in great part from the vividness of it, and the beauty of the matter it resided in, rather than from the Extent of the Luminous Body, in comparison of the small pieces of Shining Wood, I hitherto had made my Trials with; I put in the above-mentioned piece of Wood, whose luminous Superficies might be perhaps ten or twelve times as great as that which the Eye saw at once of
