Page:Proceedings of the Royal Society of London Vol 60.djvu/149

134 In each case in which K was present, the micrometer scale was set to the reading for this line, and the photograph to he reduced then adjusted until the K line was under the cross-wires of the micrometer. Each line in the spectrum was then in turn brought under the cross-wires, and the micrometer readings noted. The corresponding wave-lengths were then read off from the curve, and in this way, lists of the wave-lengths of the lines in the various spectra were compiled. These lists were then all thrown together into one table, giving the wave-lengths and intensities of all the lines recorded, and the spectra in which they appear.

For the wave-lengths thus obtained no greater accuracy than one indicated by four figures is claimed. It was my intention in the first instance to give five figures from the more elaborate tables of some of the elements given by other observers, but this had to be abandoned in consequence of the considerable variations found, in the tables between the results as given by different observers.

First, as regards the gas from eliasite. The following list gives the lines obtained in the complete inquiry after the lines due to the old gases have been eliminated. It should be stated, however, that several of the lines have wave-lengths very near those of the old gases; these have been retained when the more intense lines of the old gases are absent from the spectra. These cases are pointed out in the table.

In the case of some of the lines in the visible part of the spectrum, more accurate wave-lengths have been recorded by means of a four prism Steinheil spectroscope. These lines are indicated by (s).

Attempts have been made to concentrate the eliasite gas by the process of sparking with oxygen over potash, but the quantity of gas remaining is so small, and so largely admixed with helium and argon, that a new research, using very much more material, is essential.

It should be remarked that the list of lines which have been observed and photographed in the spectrum of the gases from eliasite represents the results of several experiments which have been made with different samples of the mineral. Some of the lineshave only been seen once, while others have' been noted several times. This suggests that the origins of the lines are very diverse, and it seems probable that some constituents of the mixture of gases obtained are absorbed by the potash in the process of sparking.

Next, with regard to the other minerals already examined. As it is impossible for me to go on with this research for the next few months, it seems desirable, in the interest of other workers, to give at the same time a complete list of the unknown lines, so far as the observations have at present gone, indicating their mineral origins, and whether or not lines nearly coincident in position have been observed in any celestial body.