1879.] on Spectroscopic Investigation. 215 



expanded bright lines ; a second pair of faint bright lines, like ghosts 

 of the first, usually coming out at the same time on the more 

 refrangible side. 



Potassium carbonate gave, besides the violet and red lines which 

 had been reversed before, the group, wave-lengths 5,831, 5,802, and 

 5,872, all reversed, the middle line of the three being the first to show 

 reversal. Also the lines wave-lengths 6,913, 6,946, well reversed, 

 the less refrangible remaining reversed the longer. Also the group, 

 wave-lengths 6,353, 5,338, 5,319 reversed, the most refrangible not 

 being reversed until after the others. Also the line wave-length 

 5,112 reversed, while two other lines of this group, wave-lengths 5,095 

 and 5,081, were not seen reversed. 



Using lithium chloride, not only were the red and blue lines, as 

 usual, easily reversed, and the orange line well reversed for a long 

 time, but also the green line was distinctly reversed ; the violet lino 

 still unreversed, though broad and expanded. Had this green line 

 belonged to cjesium, the two blue lines of that metal which are so 

 easily reversed could not have failed to appear; but there was no 

 trace of them. 



In the case of rubidium, the less refrangible of the red lines 

 was well reversed as a black line on a continuous background, but 

 it is not easy to get, even from the arc in one of our crucibles, 

 sufficient light in the low red to show the reversal of the extreme ray 

 of this metal. 



With charred barium tartrate, and also with baryta and aluminium 

 together, the reversal of the line with wave-length 6,496 was observed, 

 in addition to the reversals previously described. The less refran- 

 gible line, wave-length 6,677, was not reversed. 



With charred strontium tartrate, the lines with wave-lengths 

 4,812, 4,831, and 4,873, were reversed, and by the addition of 

 aluminium, the line wave-length 4,962 was reversed for a long time, 

 and also the lines wave-lengths 4,895, 4,868. 



On putting calcium chloride into the crucible, the line wave- 

 length 4,302 was reversed, this being the only one of the well-marked 

 group to which it belongs which appeared reversed. On another 

 occasion, when charred strontium tartrate was used, the line w^ave- 

 length 4,877 was seen reversed, as well as the strontium line near it. 

 The lines wave-lengths 6,161, 6,121, have been seen momentarily 

 reversed. 



With magnesium, when a stream of hydrogen or of coal-gas was 

 led into the crucible, the line wave-length 5,210, previously seen 

 in iron tubes, and ascribed to a combination of magnesium with 

 hydrogen, was regularly seen, usually as a dark line, sometimes 

 with a tail of fine dark lines on the more refrangible side similar to 

 the tail of bright lines seen in the sparks taken in hydrogen between 

 magnesium points. Sometimes, however, this line (5,210) was seen 

 bright. It always disappeared when the gas was discontinued, and 

 appeared again sharply on readmitting hydrogen. These effects were 



