100 YEARS AGO
Nothing is worse than fog at sea. A storm may cause discomfort, an accident may cause delay, but in neither case does the traveller feel so helpless as when his vessel is completely shut in by a dense fog. To lessen the danger which then exists, Prof. E. C. Pickering, the Director of the Harvard College Observatory, suggests, in a pamphlet just received, a method of determining the position of a vessel in a fog, based upon the velocity of sound. If two fog-horns of different pitch be placed at equal distances from the middle of a channel or entrance to a harbour, and be sounded simultaneously at regular intervals of about a minute, it will be evident that a captain of a vessel will be able to locate his position with fair accuracy by noting when the sounds of the horns are heard. If the two sounds are heard at the same instant the vessel will be in the middle of the channel, and if they are heard after one another it would be possible to judge from the interval between the two how much the vessel is out of the middle of the channel.
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