September 5, 1907] 



NATURE 



471 



velocity of sound throuj^h the unignited gas, and is 

 reflected from the ends of the tube. The flame is 

 checked while these two compression-wavfts pass 

 through the burning gases, and is then helped for- 

 ward by the waves moving in the same direction. 

 The movement then becomes unsymmetrical ; the 

 flame to the left is checked a second time before it 

 reaches its end of the tube, that to the right reaches 

 the end of the tube and sends back a strong retona- 

 tion-wave. The wave from the right i.s of greater 

 intensity and moves more rapidly than that started a 

 little later from the left, and, although the reflections 

 of these waves at first run nearly parallel, the stronger 

 gradually overtakes the weaker and coalesces with it, 

 iind the single wave continues to traverse the tube 

 from end to end. .\s many as one hundnd reflections 

 have been counted in an explosion of this kind. 

 Fig. 3 shows in outline the movements of the flame 

 and compression-waves. 



The flame in its initial stage is only very feebly 

 luminous, a fact which has led to erroneous beliefs 

 in regard to the mechanism of e.xplosion. Von 

 Oettingen and von Gernet, failing to photograph the 

 flame itself, introduced finely-divided salts into the 

 tube, and obtained brilliant pictures of the explosion 

 showing a series of parallel waves. They believed 

 that the explosion itself was quite invisible, the move- 

 ments shown in the pictures tjeing compression-waves 

 rushing through thr- burning gases after the explosion 

 was completed. 

 These parallel waves, 

 following each other 

 in cloie succession, 

 were supposed to be 

 due to " successive 

 partial explosions " 

 proceeding from the 

 spark, in accordance 

 with Bunsen's theory 

 of discontinuous step- 

 like combustion. 



The influence of 

 water vapour on the 

 combustion o f hy- 

 drogen with oxygen 

 has formed the 

 subject o f much 

 recent research. 

 .Some years ago 

 Dixon showed that 

 an electric spark 

 would fire ordinary 

 electrolytic gas 

 whether in the dried 

 or moist condition, 

 and that the velocity 

 of detonation was 

 practically unaffected 

 by the presence of 

 aqueous vapour. The 

 experiments of Baker 

 with very pure hydro- 

 gen and oxygen 

 have, however, 

 Fig. -j shown that the initi- 



ation of the flame is 

 largely influenced by the purity of the mixture. It 

 might be expected that the initial phase of the explo- 

 sion (before detonation is set up) would be modified if 

 the intcractioa of the gases depends on the presence 

 of previously formed water molecules. Dixon 

 and Bradshaw have shown by photographs that 

 this is not the case; the flame, once it has been 

 started by a spark, spreads with the same velocity in 

 the dry as in the moi-^t gases, and undergoes the 



'^- 1975. ""'oi-. 76] 



same changes in intensity. So far as the develop- 

 ment and movements of the flame are concerned, the 

 presence of water-vapour appears to make no differ- 

 ence in the union of hydrogen and oxygen. 



In a recent paper Dixon and Bradshaw have shown 

 that the compression-wave which travels in front of 

 the flame in the initial stage of the explosion mav, 

 under certain conditions, bring about the spontaneous 

 inflammation of the gases in a region of thi- tube 

 some distance 

 from the spark. 

 Fig. 4 shows the 

 explosion of hy- 

 drogen and oxy- 

 gen in a tube one 

 end of which has 

 been drawn off in 

 the blowpipe flame 

 in the manner of 

 a Carius bomb- 

 tube, so that the 

 end has the form 

 of a funnel fol- 

 lowed by a short 

 capillary. The 

 explosion is 

 started in the 

 middle of the 

 tube (s) ; almost 

 simultaneously the 

 gas inflames in 

 the capillary (c). 

 The flames meet 

 midway between 



the fine dark ver- *"'• <• 



tical lines, which 



are reference marks produced by fastening narrow 

 strips of black paper outside the explosion tube to 

 eclipse the flame as it passes. The broad band is due 

 to the clamp which held the tube in p<.isition. The 

 firing of the gas in the capillary Is caused by the 

 sudden increase of pressure in the funnel, the heat 

 of compression raising the gases to the temperature of 

 ignition. The wave produced is analogous to the 

 tidal " bore " in a funnel-shaped estuary. L. B. 



THE SEVENTH ISTEKSATIONM. ZOO- 

 LOGICAL CONGRESS. 

 THE meeting of zoologists at Boston was formally 

 convened on Monday, August 19, in the Jordan 

 Hall. Prof. .Alexander .Agassiz, as president, wel- 

 comed the members and delegates, and gave a short 

 but vivid address on th.; recent progress of oceano- 

 graphical research, especially in its zoological aspects. 

 He directed attention, for instance, to the extremely 

 interesting facts which he has discovered in regard 

 to the relations of the deep-sea faunas on the two 

 sides of the Isthmus of Panama. In a country where 

 the stranger cannot but be impressed with the amount 

 of public and private money which seems to be placed 

 at the dispo.sal of scientific institutions, it was interest- 

 ing to hear Prof. Agassiz's complaint that the 

 Government had not taken any steps to publish an 

 account of the treasures of the Albatross expedition. 

 It was one of those touches of nature which make 

 the whole world kin. 



Vice-presidents were appointed, such as Mr. Bate- 

 son (England), Prof. Hubrecht (Holland), Prof. H. F. 

 Ciborn (United States), Dr. Watase (Japan); and, 

 on the report of Prof. Blanchard, the Czar Nicolas 

 prize was awarded to Prof. Cuenot, of Paris, for his 

 research on hybrids. Special mention was also 

 made of theses by M. Loisel, of Paris, and 

 M. Standfuss, of Zurich, which did not arrive in 



