226 Miscellaneous, 



elaborately these peculiarities of bodies, and accurately to distin- 

 guish from one another by this means certain bodies susceptible 

 of such examination. They have showed that when a portion of 

 one of the metals of the alkalies or alkaline earths, or indeed of 

 almost any chemical element, is introduced into a flame, a beam 

 of light from which passes through a prism and forms a spec- 

 trum, its presence in the flame is signalized by the simultaneous 

 appearance of one or more vivid lines of light in the spec- 

 trum. Thus sodium or any of its salts in any flame, gives two 

 adjacent lines of bright orange, while lithium gives a brilliant 

 red line. They have further demonstrated, that these character- 

 istic lines are constant in position, notwithstanding very great 

 variations in the intensity of the flame, and independently of the 

 form of combination in which these substances may be supplied. 

 Still further they have established the statement that when any 

 of these metals are placed upon a fine platinum wire enclosed 

 with a similar wire in a glass tube, sparks from a Rahmkorfi''s in- 

 duction apparatus being made to pass from wire to wire, the 

 spectrum of the light so generated, is identical with that of the 

 flame into which these substances are introduced. 



Analytical processes founded on this principle prove to be of 

 unapproachable delicacy and precision. When a small portion of 

 a powder to be analyzed is projected into a flame, or better still, 

 is enclosed in the little apparatus above referred to, the presence 

 of considerably less than one hundred thousandth part of a grain 

 of sodium, or potassium, or lithium, can be detected with cer- 

 tainty by the practised observer. Already have investigations of 

 this nature brought to view at least two new metals ; one, caesium 

 belonging to the calcium group of metals, and one, yet unnamed, 

 belonging to the sulphur group of elements. The former, discov- 

 ered by the originators of this mode of investigation, announced 

 itself by two blue lines, one especially bright being towards the 

 violet end of the spectrum. The latter, found associated with 

 selenium and tellurium, by Crookes, signalized its presence by a 

 remarkable and unmistakable bright green line, leading to its 

 identification as a hitherto unknown element. 



The same investigators show that a flame giving any bright 

 line in the spectrum, while transparent to other light, is opaque 

 to that particular ray. Hence a kind of negative spectrum of a 

 fliame may be produced in which the bright lines are replaced by 

 dark ones, by placing behind it a much more brilliant light giving 

 a continuous spectrum. Thus magnesium gives when present in 



