Page:Proceedings of the Royal Society of London Vol 60.djvu/509

Rh In continuation of investigations communicated to the Royal Society in 1879* and 1881,f on the effect of liigh-tension electricity on the line spectra of metals, I have recently used a more powerful current and larger jar surface than th at I formerly employed.

The former work consisted in noting (1) the lines brightened m passing a spark in a flame charged w ith metallic vapours, and (2) the lines brightened on passing from the arc to the spark. It was found, in the case of iron, that two lines in the visible spectrum at 4924’1 anc 5018-6, on Rowland’s scale, were greatly enhanced m brightness, and were very important in solar phenomena.

The recent work carries these results into the photographic region. The result is interesting and important, since seven additional lines have been found to have their brightness enhanced at the highest temperature. These, as well as the two previously observed, are shown in the following table, which also indicates the behaviour of the lines under different conditions, as observed by Kayser and Runge (K and R) and myself (L) in the arc, and by Thalen (T) and myself in sparks :—

Lines of Iron which are enhanced in Spark.

Wavelength. Intensity in flame. Intensity in arc (K and K). Max. = 10. Length in arc (L). Max. = 10. Intensity in spark (T). Max. = 10. Intensity in hot spark (L). Max. = 10. 4233 -3 j 1 _ — 4 4515-5 — 1 — — 4 ! 4520 -4 — 1 — — 2 i 4584-0 — 2 4 — 7 i 4924 -1 — 1 3 6 6 i 5018-6 4 ____
 * 1
 * 4508'5 — 1 — — 4
 * 4522 -8 — 1 3 — 4
 * 4549 -6 — 4 5 — 6

Combining this with former results, we seem justified in concluding that, in a space heated to the temperature of the hottest spark, and shielded from a lower temperature, these lines would constitute the spectrum of iron.

t Ibid., 1881, toI. 32, p. 204.
 * * Roy. Soc. Proc.,’ 1879, vol. 30, p. 22.