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placed; and of two tubes fixed into the plate, one being a 

 telescope having a magnifying power of 40, moveable with a 

 slow-motion screw about a vertical axis placed in the centre 

 of the plate, and the other being a tube carrying at one end 

 the slit, furnished with micrometer screw^ through which the 

 beam of light passed, and at the other end an object-glass 

 for the purpose of rendering the rays parallel. The luminous 

 vapours of the metals under examination were obtained by 

 placing a bead of the chloride or other salt of the metal on a 

 platinum wire, between two platinum electrodes, from which 

 the spark of a powerful induction coil could be passed. In 

 order to obtain a more intense, and therefore a hotter spark 

 than can be got from the coil alone, the coatings of a Ley den 

 jar were placed in connection with electrodes of the secondary 

 current respectively. When this arrangement was carefully 

 adjusted, the two yellow sodium lines were observed to be 

 separated by an apparent interval of two millimetres, as 

 seen at the least distance of distinct vision. 



The position of the blue line, or rather blue band of 

 lithium, was then determined with reference to the fixed 

 reflecting scale of Steinheil's instrument, by volatilising the 

 carbonate of lithium in the first place on a platinum wire 

 between platinum electrodes, and secondly on a copper wire 

 between copper electrodes. A bead of pure chloride of 

 strontium was then placed on new platinum and copper wires 

 between two new platinum and copper electrodes, and the 

 position of the blue line Sr S read off upon the same fixed 

 scale ; a difference of one division on the scale was seen to 

 exist between the positions of the two lines, the lithium line 

 being the more refrangible. The salts of the two metals 

 were then placed between the poles at the same time, and 

 both the blue lines were simultaneously seen, separated by a 

 space about equal to that separating the two sodium lines. 

 When experimenting with this complete instrument, we were 

 unable to observe any other blue lines in the pure lithium 



