Micrometrical Measures of Gaseous Spectra Under High Dispersion

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1886 edition. Excerpt: ...dispersion of my present Prisms below the Green is too small; ('2) Above the Green the definition is not sufficiently good; (3) Towards either end of the Spectrum the illumination of my existing sparking apparatus is not suificiently bright; and (4) It is very difficult to get those bands perfectly free from impurities of CH, H, and other gases. I will therefore at present proceed to a provisional termination of the CO subject, by means of a few words on some general characteristics of that compound gas in vacuum tubes. A small pressure of the gas, say 0'25 inch, seems to be most suitable for securing a maximum of brilliancy conjoined to stability. For higher pressures, say 1 inch, 2'5, 5'0, or 12'5 inches, simply show the same spectrum, but fainter and fainter as the pressure is greater; while lower pressures, say 0'1 inch or under that, though exceedingly brilliant for a time, are very apt to get their tubes overheated and loosened at their electrodes with loss of illuminating power altogether. To prevent this catastrophe, the electrode ends of the tubes, whether with platinum wires as usual passing through them, or coated only with a film of silver outside, have been made to dip into vulcanite insulated basins of water, and receive their electric charge from thence; but the illumination was never at its best in that manner, the whole apparatus sometimes became inconveniently charged; and with the silver coated tubes, the glass was actually perforated sooner or later. Some of the best exhibitions, however, of the CO spectrum, have been the unintended ones; as of tubes prepared with Oxygen alone; and showing at first the Oxygen spectrum, but that changing during use into CO; and always more and more quickly or inevitably, the weaker the...