When I say that the thunder was _simultaneous_ with the lightning, I speak as an inexact person. My meaning is that the time which elapsed between seeing the flash and hearing the report was inappreciable to me. I wish to speak with all possible precision, and there are two points with regard to this storm upon which I can speak with some accuracy. The first is in regard to the distance of the lightning from our party. We _might_ have been 1100 feet from it if a second of time had elapsed between seeing the flashes and hearing the reports; and a second of time is not appreciated by inexact persons. It was certain that we were sometimes less than that distance from the lightning, because I saw it pass in front of well-known points on the ridge, both above and below us, which were less (sometimes considerably less) than a thousand feet distant. Secondly, in regard to the difficulty of distinguishing sounds which are merely echoes from true thunder, or the noise which occurs simultaneously with lightning. Arago entered into this subject at some length in his _Meteorological Essays_, and seemed to doubt if it would ever be possible to determine whether echoes are _always_ the cause of the rolling sounds commonly called thunder.(83) I shall not attempt to show whether the rolling sounds should ever, or never, be regarded as true thunder, but only that during this storm upon the Matterhorn it was possible to distinguish the sound of the thunder itself from the sounds (rolling and otherwise) which were merely the echoes of the first, original sound. At the place where we were camped a remarkable echo could be heard (one so remarkable that if it could be heard in this country it would draw crowds for its own sake); I believe it came from the cliffs of the Dent d’Hérens. It was a favourite amusement with us to shout to rouse this echo, which repeated any sharp cry, in a very distinct manner, several times, after the lapse of something like a dozen seconds. The thunderstorm lasted nearly two hours, and raged at times with great fury; and the prolonged rollings from the surrounding mountains, after one flash, had not usually ceased before another set of echoes took up the discourse, and maintained the reverberations without a break. Occasionally there was a pause, interrupted presently by a single clap, the accompaniment of a single discharge, and after such times I could recognise the echoes from the Dent d’Hérens by their peculiar repetitions, and by the length of time which had passed since the reports had occurred of which they were the echoes. If I had been unaware of the existence of this echo, I should have supposed that the resounds were original reports of explosions which had been unnoticed, since in intensity they were scarcely distinguishable from the true thunder; which, during this storm, seemed to me, upon every occasion, to consist of a single, harsh, instantaneous sound.(84)