142 EFFECT OF HIGH TEMPERATURE PART i. 



condensed into a double line of intense brilliancy on a 

 dark ground. The iron spectrum on the contrary is 

 crossed by bright lines of all intensities and colours in 

 such multitudes, that their number has not been ascer- 

 tained. The calcium spectrum has one very bright green 

 band in the orange, a red line in the yellow, and a well- 

 defined yellow line in the indigo. As already mentioned, 

 the red and orange parts of the strontium are crossed by 

 many red lines separated by dark intervals ; there is a 

 bright blue line between the orange and yellow, and an 

 orange line in the blue. One intense crimson band in 

 the orange characterises the lithium spectrum. Seven 

 broad green bands stripe the yellow and a part of the 

 green, in the barium spectrum, and that of magnesium 

 has many green bands and lines. 



All of these were determined by the heat of white coal 

 gas flame, which amounts to 2350 Cent., and at the time 

 MM. Bunsen and Kirchhoff were not aware that by an 

 increase of temperature new bright lines were added 

 to some of the spectra. That discovery was made by 

 Professor Tyndall, while examining the spectrum of 

 chloride of lithium, which with the low temperature has 

 only one crimson band in the orange, but with the hotter 

 flame of hydrogen gas, amounting to 3259 Cent., an 

 orange line appeared in the yellow, and when Mr. Tyndall 

 employed the electric lamp, 9 the spectrum acquired a 

 broad brilliant blue band between the orange and yel- 

 low, while the crimson band remained unchanged. 

 Professors Eoscoe and Clifton confirmed Tyndall's dis- 

 covery, and upon comparing the spectra of strontium 

 and lithium, they found where only one prism was em- 

 ployed that the blue line of lithium appeared to coincide 

 with the blue line, delta, of strontium; but with an 



9 The light of the electric lamp is produced by an apparatus which suc- 

 cessively makes and breaks an electric current, whereby the terminal char- 

 coal points become red-hot. 



