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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 Leyden 
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 Steinlieil’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 8 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 
