Nature . assingthrough an envelope of cooler vapours, and on thisaccount absorption phenomena are produced. Our knowledge of the chemistry of the sun and starsis founded upon the coincidence of the bright lines understand the theorem, it is absurd to thinkthat even average schoolboys who have been six yearsat mathematics can understand how logarithms arecalculated. But if a schoolboy has been told what alogarithm means, and if he can extract a square root bythe ordinary arithmetical method, and especially if he hashad a sensible teacher and been allowed to use tables ofloga
Nature . assingthrough an envelope of cooler vapours, and on thisaccount absorption phenomena are produced. Our knowledge of the chemistry of the sun and starsis founded upon the coincidence of the bright lines understand the theorem, it is absurd to thinkthat even average schoolboys who have been six yearsat mathematics can understand how logarithms arecalculated. But if a schoolboy has been told what alogarithm means, and if he can extract a square root bythe ordinary arithmetical method, and especially if he hashad a sensible teacher and been allowed to use tables oflogarithms, 1 think that he will have no difficulty irkunderstanding the following method, and will ratherenjoy working at it a little. Let him find 10=, lOA, loiS^ ioi/6, 101/3=, by re-peatedly extracting square roots, getting out his answersto five significant figures, say. Let him now by multi-plication calculate 103/32, 105/32, (ic, right up to 10. Hethus has a table of which I give the beginning and -The coinciden seen in our laboratories with the dark lines noted in thespectra of those celestial bodies. The diagram showsthe coincidence in the case of the double orange lineof sodium vapour with dark lines in the spectrum ofthe sun. Now if my reader has not hesitated to invest his orher sixpence in a prism, and has had the patience (noother quality is needed) to do what 1 have suggested, theway is open to read with intelligence most books in-volving spectrum analysis which he or she is likely tocome across ; terms such as Spectrum Continuous spectrum Grating Prism Spectroscope Slit Line spectra Fluted spectra Discontinuous (or selective) spectrumFraunhofer linesWave-lengthRadiationAbsorptionSeries should now have acquired a definite meaning, and 1trust the expressiveness of the terms will be acknow-ledged while they are accepted as part of the futuremental stock-in-trade. NORM.\N LOCKVKR. TO CALCULATE A TABLE OF LOGARITHMS. T 7 AVTNG been asked to give a short course of l
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