Page:Transactions of the Provincial Medical and Surgical Association, volume 4.djvu/207

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The elevation of the village of Great Malvern is about 520 feet; it is therefore necessary to add about .570 in. to all the heights observed. If the reader should take the trouble of doing this to any of them, he would immediately perceive the very slight differences in the fluctuations of the barometer in London and Malvern.

In looking over the various daily details from which the foregoing mean barometrical heights have been deduced, the coincidence in the movements of the two barometers was so constant, that I have taken pains to determine accurately this point; and upon comparing the daily fluctuations, for a whole month, at the same time at each place, after every necessary correction, the variation between the simultaneous movements of each has very generally not been more than a few hundredths, a result peculiarly establishing the constant magnitude of the atmospheric movements.

There are many minor circumstances likely to introduce discrepancies in any comparison between the heights of two barometers distantly situated, and noted by different persons; thus they may not be observed at precisely the same period, and this, should they happen to be rising or falling rapidly at the time, would introduce some error; again, at the time of observation, one person may give a tap with his finger to the tube—the other may not, which will sometimes make a difference of some hundredths, the mercury, often adhering slightly to the glass, resuming its proper indication when gently moved or shaken.

From these considerations (to say nothing of the