HartLEy—On some Devices facilitating the Study of Spectra. 239 
fuses upon the surface. The shape of the flame is a cone about 
25 mm. high, and therefore pyramidal. Draughts do not 
affect the flame. In the Mecke burner, fused alkali and alkaline 
earth-salts are easily examined on platinum wire, hard asbestos 
fibres, quartz fibres, or on tobacco-pipe. It is, of course, necessary 
to ascertain what spectrum-lines the support yields, and eliminate 
the lines or bands from the spectra subsequently observed. Quartz 
fibres and platinum obviously yield nothing. Fusible silicates, 
such as lepidolite, show the spectra of potassium, lithium, and, 
with a wide slit, even of rubidium. A convenient way of 
examining solutions is toremploy a clay tobacco-pipe, to plug the 
mouthpiece of the pipe with two or three asbestos fibres, and to 
pour the solution into the bowl. By inclining the pipe, the solu- 
tion soaks through the asbestos, the water evaporates, and the salt 
fuses on the fibres. Similarly, a piece of quartz tube is drawn 
out to a capillary point, the end being left open; the solution 
then issues in drops, which dry upon the point of the tube; it is 
the solid salt, and also spray from the solution, which yields the 
spectrum. ‘The quartz is unbreakable by the contact of the hot 
material with a cold solution. When even white-hot, it may be 
dropped into cold water without cracking, or into hydrochloric 
acid, in order to cleanse it. 
The Mecke blast-burner.—This modification, in addition to the 
injector, has an air-jet placed higher up in the tube. The air- 
blast must be supplied with a regulated constant-pressure, which 
may be obtained in any way, as by bellows, a rotary fan, or 
tromp; but the pressure should not be less than two kilogrammes 
per square centimetre. With water direct from the high-pressure 
mains, the water-blower is satisfactory ; but the instrument should 
be fitted with a pressure-gauge. A blower fitted up twenty-five 
years ago has been found generally effective. The essential parts 
are a Korting’s jet, soldered on to a water-tap, to which again the 
inlet-tube of the blower is soldered. The air-reservoir is a tube 
4 feet long by 3 inches broad. Platinum wire, of the usual 
thickness suitable for spectroscopy, is easily melted in the flame 
at its hottest part; and therefore quartz-fibres are a suitable 
material to use as supports. ‘To convey some idea of the advan- 
tages gained by the use of these burners for spectroscopic work, 
I may mention that the use of fused salts or infusible compounds 
