370 Dr. Karl Heamann's Contributions to 



Further, the fact experimentally proved, that the surface of a 

 body heated to redness may become covered with soot, is op- 

 posed to Frankland's hypothesis : if the deposition consisted of 

 condensed hydrocarbons, it could only take place upon surfaces 

 relatively colder than the flame itself. If the space immedi- 

 ately over the flame of burning turpentine be examined, it is 

 seen to contain flaky particles of sooty matter. A hydrogen- 

 flame brought into this layer becomes surrounded by a conti- 

 nuous luminous mantle ; the flame of a Bunsen lamp becomes 

 crowded with glowing particles. No glowing particles can 

 be distinguished by the eye or by means of the microscope in 

 a luminous gas-flame, by reason of the rapidity with which 

 the current of gas is carried upwards. These small particles 

 are stopped in their upward course by any solid body brought 

 into the flame, or by the comparatively still layers of air ; they 

 thus become more compact and dense, and so bring about the 

 deposition upon themselves of further numbers of particles 

 until there is finally formed a visible cloud of soot or smoke. 

 A solid body, or even a layer of air, while stopping the rush of 

 solid particles, simultaneously lowers the temperature of the 

 flame. 



In order to render visible the production of masses of solid 

 matter, two blowpipe-nozzles, through each of which a stream 

 of gas issued, were arranged horizontally opposite to one 

 another By regulating the distance between the nozzles a 

 perfectly circular homogeneous flame was obtained ; by bring- 

 ing the nozzles rather nearer to one another and slightly altering 

 their inclination, the flame assumed a half-moon shape. The 

 lower part of this flame was but slightly luminous, but was 

 filled with little glowing points (fig. 1, Plate II.). The flame 

 being in a kind of whirling motion, these little points were 

 swept upwards and passed away as sparks from each horn of 

 the half-moon. By bringing a porcelain plate over these 

 points, the little particles were obtained in the form of coarse- 

 grained soot. The appearances described become more appa- 

 rent by causing the gas to issue under diminished pressure; 

 but in this case the regulation of the flow is more difficult. 



Another experiment was arranged in which the little par- 

 ticles of carbon were caused to form a larger and visible mass 

 by projection against a solid body. A platinum basin hung 

 vertically was heated on the concave side by means of a Bun- 

 sen's lamp ; a coal-gas flame about 5 centims. in length was 

 caused to issue from the narrow circular orifice of a tube which 

 was held by a clamp, and directed so that the flame struck the 

 basin a little below the centre. By regulating the distance 

 between this tube and the basin, a halfmoon-ehaped flame 



