Abstract
BY the direction of C. P. Patterson, the Superintendent of the U.S. Coast and Geodetic Survey, I have long been engaged in the precise measurement of a wave-length of light, in order to obtain a check upon the secular molecular changes of metallic bars used as standards of length. In advance of the publication of this work it may be useful to say I have found that the closest-ruled diffraction-plates by Mr. Lewis Rutherfurd have a mean width of ruling which varies in different specimens from 68078 to 68082 lines to the decimetre, at 70° F. There is a solar spectral line, well suited for precise observation, whose minimum deviation with one of Mr. Rutherfurd's plates in the spectrum of the second order with the closest ruled plates is 45° 01′ 56″ at 70° F. I would propose that this line be adopted as a standard of reference by such observers of wave-lengths as desire to escape the arduous operation of measuring the mean width of their rulings; for by means of the measures which are shortly to be published it will be possible to deduce from the minimum deviation of this line produced by any given gitter, the mean width of that gitter, and consequently the wave-length of any other line whose deviation has been observed with it. The accuracy of this method will greatly exceed that of assuming Ångström's measures to be correct. The wave-length of the line in question (still subject to some corrections which may be considerable) is 5624825. Ångström gives 562336.
Article PDF
Rights and permissions
About this article
Cite this article
PEIRCE, C. Width of Mr. Rutherfurd's Rulings . Nature 24, 262 (1881). https://doi.org/10.1038/024262a0
Issue Date:
DOI: https://doi.org/10.1038/024262a0