Page:Proceedings of the Royal Society of London Vol 60.djvu/148

Rh

In the first note of the series “ On the New Oases obtained from Uraninite,” by the distillation method, I remarked* “ I have already obtained evidence that the method I have indicated may ultimately provide ns with other new gases, the lines of which are also associated with those of the chromosphere.”

In a subsequent paper “ On the Gases obtained from the Mineral Eliasite,” I gave a list of several lines unknown to me, and suggested that they might indicate the existence of a new gas or gases in that mineral, and I addedl Although the evidence in favour of a new gas is already very strong, no final verdict can be given until the spectra of all the known gases, including argon, have been photographed at atmospheric pressure, and the lines tabulated. This part of the inquiry is well in hand.”

The inquiry above referred to has now been completed and in the following manner:—

Photographs were taken of the spectra at atmospheric pressure of nitrogen, oxygen, chlorine, carbonic anhydride, coal gas, sulphuric anhydride, phosphoretted hydrogen, and argon, these being the gases which, from the experience t-lius far acquired, are likely to be associated with those given off by minerals. In addition to these, the lines of mercury, potassium, and platinum, were also photographed. The lines of platinum are alwrays present in the spectra for the reason that the spark is passed between platinum poles, while the lines of mercury or potassium frequently appear according as the gases are collected over mercury or potash.

The spectroscope employed has a collimator and camera with object glasses of 3 in. aperture, and focal lengths of 5 ft. and 19 in. respectively. Two prisms of 60° were used, giving a length of spectrum, of about 1‘75 in. between K and D.

In order to facilitate the reduction of the photographs, the solar spectrum was photographed under exactly similar instrumental conditions. Micrometric measures were made of H and K, and other well-known lines throughout the spectrum, and by means of these and Rowland’s wave-lengths, a curve was carefully constructed.

It may be incidentally mentioned that in the photographs of the spectra of gases at atmospheric pressure, H and K are generally present as pole lines, being probably due to an impurity of calcium in the platinum poles.

f ‘ Roy. Soc. Proc.,’ vol. 59, p. 3.
 * ‘ Roy. Soc. Proc.,’ vol. 58, p. 70.