on the Equivalent and Spectrum of Cesium. 97 
The equivalent number 133, brings cesium into a triad with 
rubidium and potassium. We have then two alkali triads, viz: 
lithium, (eq. 7), sodium (eq. 23) and potassium (eq. 39°1), 
£9? 9s 
and potassium, rubidium (eq. 85°36) and cesium. 
me 1 rine 86 
further that some of those figured by K. & B.} are not mapped 
in their correct positions. To enable other chemists to compare 
their cesium preparations with ours, we will attempt to describe 
the caesium Spectrum as seen in our instrument, which has a 
Single flint glass prism. 
._veginning at the left or red extremity of the spectrum, we 
Will indicate the lines in the order of their occurrence by Roman 
numerals; I. is a red line of medium brightness nearly equidis- 
‘ant between the Fraunhofer lines a and B; IL. isa bright line 
Partly coincident with, but slightly to the left of and narrower 
TOW spaces, and which are represented well in the spectrum plate 
of Kirchhoff and Bunsen, thou h placed a trifle too far to the 
i t. Then, after an interval scarcely wider than the lines 
©mselves, come XII, and XIII , Which are very near each other. 
