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The Observer, M. Estienne, notes, that, when he made this Observation, the River of Chartres, which runs very near from South to North, was betwixt him and the Rainbow; and that he stood Level with this River, whence he was distant not above 150 paces: which he adds, that the Curious may the better judge of this Observation.
This was imparted by Dr. Wallis in a Letter, written at Oxford, May 12. 1666. to the Publisher, as follows:
I should scarce have given you so soon the trouble of another Letter, were it not for an Accident which hapn'd here May 10. I had that afternoon, about 4 of the clock heard it thunder at some distance. About 5 of the clock the Thunder coming nearer to us, it began to rain, and soon after (the rain withal increasing) the Thunder grew very loud, and frequent, and with long ratling Claps (though not altogether so great, as I have some other times heard:) and the Lightning with flashes very bright (notwithstanding the clear day-light) and very frequent, (when at the fastest, scarce a full minute between one flash and another; many times not so much, but a second flash before the Thunder of the former was heard:) The Thunder for the most part began to be heard about 8 or 10 second minutes after the flash; as I observ'd for a great part of the time by my Minute-Watch: but once or twice I observ'd it to follow (in a manner) immediately upon it, as it were in the same moment; and the lightning extream red and fiery. I do not use to be much apprehensive of Thunder and Lightning, but I was at this time (I know not well, why?) very apprehensive, more than ordinary, of mischief to be done by it, for it seem'd to me to be very low and near us (which made me so particular, as to observe the distance of the flash by the noise) and very frequent, and bright, so that, had it been by night as it was by day, it would have been very terrible. And, though I kept within doors, yet I sensibly discover'd a stinking sulphureous smell in the Air. About 7 of the clock it ended, before which time I had news brought me of a Sad Accident upon the
