form the subject of another com m unication dealing w ith the chemistry of the process.
Some of the photographs were rem arkably fine in definition, and they extended from the less refrangible lim it of th e red rays to th e ultra-violet, about w ave-length 3240.
It may be m entioned here, however, th a t every line and band in the different spectra was identified. Some of th e photographs afforded evidence of very unusual constituents in the m ixture of gases and vapours, w hich by th eir com bustion and incandescence give the Bessemer flame. The identity of these could have been established only by means of very complete investigation of oxyhydrogen blowpipe spectra. A part from all technical considerations which were kept in view, and of such purely scientific questions as were involved in sim ilar previous researches carried out by one o f us, the examination of these spectra was of great interest, more especially because of the proof of th e rare element, gallium , being present in the Bessemer metal, and in the roasted ore from which it was extracted. I t was shown by very careful analyses that the gallium was concentrated in th e iron, b u t all details of the operations involved in its separation and of th e quantitative determinations are reserved for a future communication.
The evidence of the existence of gallium in th e ore and in the metal rests on the measurements of the w ave-lengths of the lines in a large number of photographed spectra and upon the relative strengths of the lines in the different materials examined and in the precipitates obtained therefrom.
The following examples show the nature of this evidence:—
1. Evidence from the Bessemer Flame Spectra.
Seventy-six of the photographed spectra of the Bessemer flame contain a strong line with w ave-length about 4171‘5, which does not appear to be related to any other line in these spectra, and belongs, therefore, to some other element than those otherwise identified.
2. Evidence from the Spectrum of the “ Mixer Metal and of the different substances separated by its Chemical Treatment.
The “ m ixer m e tal” heated in the oxy-hydrogen flame gives a spectrum of iron w ith a strong line having a wave-length of 4171'6.
The residue left after dissolving the iron by boiling w ith hydrochloric acid also gives this line 4171*6 very strongly.
Precipitates obtained by boiling the solution of the iron with ammonium acetate give the line 4171*6 and also a weaker line, wavelength 4032*7.
