Abstract
THE application of Fourier's harmonic analysis to weather phenomena has revealed many outstanding periodicities. To those who feel that the next step should be directed towards understanding the cause of these periodicities, rather than the evaluation of yet more, the invention of mechanical aids to ‘periodicity hunting’, such as Abbot's periodometer, will naturally make little appeal (Smithsonian Miscell. Coll., vol. 87, No. 4 (Pub. 3138): “The Periodometer, an Instrument for Finding and Evaluating Periodicities in Long Series of Observations”. By Dr. C. G. Abbot). The device is one for avoiding numerical computation in studies of this kind. It does not detect periodicities; that has to be done by inspection of the statistical material. This step involves a personal factor. Given any suspected periodicity, the machine shows to what extent this appears consistently throughout the material, and determines the shape of the curve of variation of the element over this period. The reality of the periodicity is judged from the shape of this curve. Having decided that it is real, the operator is then able, with the aid of the machine, to eliminate this periodic variation, and so gets a residual curve that is scrutinised afresh for other periodicities. The curve of variation may depart widely from a simple sine curve, and this method of analysis therefore differs from the classical Fourier process, and on account of the presence of the personal factor will give different results when different workers use the same material. The ultimate test of merit is, of course, whether the method will lead to greater knowledge of underlying physical causes, and it remains to be seen whether this will be the case. The cost of production of the first periodometer was apparently a thousand dollars, the money being provided by the Research Corporation of New York.
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Evaluating Periodicities by Machinery. Nature 129, 684 (1932). https://doi.org/10.1038/129684b0
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DOI: https://doi.org/10.1038/129684b0