Papers on meteorology : relating especially to the climate of Britain, and to the variations of the barometer / by Luke Howard.

  • Luke Howard
Date:
1850-1854
Catalogue details

Licence: Public Domain Mark

Credit: Papers on meteorology : relating especially to the climate of Britain, and to the variations of the barometer / by Luke Howard. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    51/174 page 41
    —an investigation which he was led to undertake in consequence of being engaged in completing another paper for the Society, exhibiting a system of barometric averages ruled by the moon’s place in declination, to which we shall refer in the next place. The moon having been on the equator, December 3rd, 1821, twenty-two days before * the crisis of the great depression of the 25tli, and also on the 22nd of October 1840, twenty-two days before that of the great depression of November 13th, the author laid down on a scale of the barometer twenty-nine days of variation of the daily mean height in each case, the diagram thus produced being given in the paper. Referring to this, he observes, “ It will be seen at once, that, thus placed together, the two variations agree (with each other and with the spaces of the period) in a manner which can be attributed to nothing (as the remote or ruling cause) but the moon s change of place in declination.” He points out, again, that “ there is a swell in the curve of variation, in each case interrupting the continued descent, or rather pre- ceding it, which corresponds in like manner with a south declination in 1840, and a north in 1821;” and that, moreover, the two curves correspond in figure generally, there being in each the same number of nearly simultaneous changes of direction, which set out at the beginning of the period from the same point, and return after the recovery very nearly to the same point of the scale again. With all these features of agreement, at once with the assigned cause, and with its period and division of time, Mr. Howard thinks no astronomer will be found hesitating as to the actual connection, but will at once pronounce these movements an affair of lunar declina- tion—a problem which is to be investigated and solved on no other than astronomi- cal principles. The entire result of this investigation, he remarks, proved more striking than he had expected, the movements of the barometer in these two cases classing decidedly with those of the periods he had taken from the years 1807 and 1816, to exemplify this kind of variation in the “ Climate of London ” ;—and as already discussed in the present Section. Adverting, in conclusion, to the apparent discrepancy, “that in one case the moon was approaching from the south during the fall of the barometer, and in high north declination at the crisis ; in the other, receding southward and over a distant latitude on that side the equator at the time of the greatest manifestation [through the barometer] of its power here,” he refers in explanation to the nature and movements of the great tidal wave in the ocean, following new and full moon alike; admitting, however, that the winds may or may not be found a principal mediate cause of these variations, under the directing power of our attendant planet. G
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