1872.] Capt. W. A. Ross on Pyrology, or Fire Analysis. 451 



be observed to be broken up by the blast at the under extremity, the sides 

 remaining intact, so that the form is now that of a hollow cylinder. 



7. Very different is the pyrocone produced by the attempt to blow into 

 the natural one afforded by the flame of ignited oil*, wax, coal-gas (not 

 previously mixed with air as in the Bunsen burner), or other dense hydro- 

 carbon. The blast cone no longer penetrates the blue flame, but moves 

 above it, drawing out, as it were telescopically, a solid pyrocone from 

 under its base, so that the two cones are no longer synaxial but conjunc- 

 tive (fig. 1). 



8. If we view this pyrocone from above, the diagram (fig. 2) is some- 

 thing like what we see. All ascending heat from the lamp is completely 

 stopped ; whereas we could not view the spirit-pyrocone from alike position 

 without burning the face, because in the first case the natural pyrocone is bent, 

 as it were, under the blast, but in the second merely bored through by it. 



9. It will be seen from fig. 2 that the hollow nucleus of the natural pyro- 

 cone, which we have assumed to be filled with unburned gases, is traversed 

 over its whole length by the blast cone from the jet, showing the wick of 

 the lamp underneath as a black band, the breadth of which is directly pro- 

 portional to the diameter of the base of the blast cone, .and therefore in- 

 versely so to the strength of the blast, which, blowing in the short side a 

 of the blue or hydrocarbonous perimeter into its long sides c, c, causes 

 these latter to rise slightly like flame-walls on either side, and draws them 

 along with it until they combine at b to form a solid pyrocone underneath 

 it, as above described. 



10. If the short side a be burst by the insertion of the jet, instead of by 

 the blast, the shape of the latter, as seen from above over the wick, is that 

 represented in fig. 3, the size and power of the resulting pyrocone being 

 immensely diminished. 



11. If, therefore, the blast in pyrological operations were driven through 

 the long axis of the oil- or gas-lamp artificial pyrocone, as is generally 

 assumed, and as is undoubtedly the case with the spirit-cone, we could not 

 (1) see the lamp-wick as through a transparent medium like air, and (2) 

 the heat ascending from the upper part of the pyrocone would be felt upon 

 the face of the operator stooping over it ; but it must be here observed 

 that, to produce these effects, the volume and strength of the blast must 

 bear a certain proportion to the size of the natural pyrocone. 



12. It would be reasonable to expect from the above that the spirit- 

 and oil-lamp pyrocones should possess different properties, and this is the 

 fact. The pyrogenical or artificial cone of the former cannot, or can but 

 feebly, attain the results produced by the latter. Filled with breath-vapour, 

 instead of being solid, it has too much heating-power, while the enclosed 

 gases interfere both with the oxidation and the reduction of the subject of 

 analysis. 



* Cocoa-nut oil (if it bo perfectly pure) affords by far the best pyrocone, and coal- 

 gas almost the worst, for the purposes detailed in paragraph 15. 



2 L 2 



