238 Scientific Proceedings, Royal Dublin Society. 
spectrum. Oyanite is not always procurable, but carborundum is 
now an article of commerce. 
Carborundum.—This gives no spectrum in the oxyhydrogen 
flame; it is incombustible, and quite infusible. This material 
in a form adapted for supports is manufactured by the Car- 
borundum Company for other purposes, the small crystals being 
mixed with porcelain clay, and fired at a high temperature. 
Thin, flattened pieces, four inches in length and ;), of an inch in 
thickness, are sold as silversmiths’ stones. It is advisable that this 
material be cautiously introduced into the flame. 
Quartz fibres and thin rods.—At the melting-point of platinum 
quartz only softens ; hence this material, which is now manufactured 
by Messrs. Johnson & Mathey, in the form of rod and tube, 
is available for use. The quartz, as a rule, gives no impurity 
lines. 
The Mecke burner.—In all the various forms of smokeless 
burners which have been devised, the chief defect lies in the small 
area of the cross-section of the flame, which provides the maximum 
temperature ; great variations in temperature arise from the 
irregularity of the flame, when subject to the influence of draughts, 
especially horizontal currents of air. From these defects the 
Mecke burner is entirely free; and for ordinary spectroscopic 
purposes I can recommend no other. Its construction is that 
of a Gifford’s injector, the current of gas injecting into the tube 
the requisite amount of air necessary for its complete combustion. 
In order to admit of the gas and air being mixed together, two 
metallic gratings are placed within the tube of the burner; and 
about half an inch above the upper grating a cap consisting of 
a third grating is fitted. As the upper part of the tube is 
choked by the gratings, it is expanded to compensate for this. 
To ignite the mixture of gas and air, the match-flame must not 
be held above, but close to the grating. Supposing the diameter 
of the top of the burner be two centimetres, the gaseous mixture 
is seen to burn from about thirty-seven little jets, each of which 
shows a green cone if the air is excessive, but a blue one if the 
mixture is of the right nature to obtain the highest temperature. 
The maximum heating effect is from two to three millimetres 
above the grating ; and it is equable across the whole diameter 
of the tube. Platinum wire of the ordinary thickness just 
