46 



NATURE 



S^Nov. 19, 1874 



in the burner by an inferior mixture whicli succeeds it at a slower 

 speed. 



From the following experiment and considerations I am in- 

 clined to attribute the observed action of the disturbed flame 

 almost entirely to direct influence of the sound upon the ^'as-jet, 

 rather than to its eflect upon the cm'rent of air passing through 

 the conical cap of gauze that surrounds it. The current through 

 the gauze is so slight that ascending smoke, slowly creeping round 

 it, is not visibly drawn into its meshes. The sensitive action of 

 the flame remains equally perfect when all but a very small 

 aperture of the gauze is closely covered with thin sheet india- 

 rubber. To determine if a naked jet, unsurrounded by wire- 

 gauze, would by itself produce a flame so sensitive, I easily 

 obtained with a Ladd's tapering brass jet aflame of this descrip- 

 tion. I^ayingitupon its side with its point inchning downwards, 

 and inserting this into a brass tube about ^ in. wide and 15 in. 

 long, also inclmed, the flame at the lower end of this tuhe, 

 when full gas was used, resembled a Bunsen- flame ; but if the 

 gas-supply is lowered, it becomes luminous ; and at the lowest 

 point at which it will continue to burn, the slight current in the 

 tube appears to consist only of nearly pure coal-gas, and is of 

 course {a useful point in the manipulation) quite inexplosive. A 

 stamp, a cough, or other deep-pitched sound, as the exclamations 

 Oh ! and Ah ! caused this flame to emerge from its hiding-place 

 in the end of the tube into which it had retreated, and to rise in a 

 tall tongue of light. It was not sensitive to notes of high pitch, 

 to a his.s, nor to some of the acuter vowel-sounds of the voice, 

 unless very strongly uttered ; but a short groan or growl called it 

 forth at once. The lower the speed of a jet the slower, possibly, 

 may be the vibrations required to affect and sensibly to disturb 

 its equilibrium. With a very perfect gas-meter the question might 

 also be decided how much of the large additional gas-volume in 

 the flame which occasionally reached a height of about 2 in., and 

 which could easily be maintained permanently at a height of 

 about I in. by continued stamping on a stone floor, is derived 

 from the gas-jet itself, and how much from increased admixture 

 with it of the surrounding air. As the jet is constantly being 

 bent, as it leaves the fixed nozzle, into the shape of a corkscrew, 

 or of some other wave-curve by the air-vibrations, it probably 

 draws more air along with it, in the same way that a coarsely 

 twisted rope in hair rope pumps raises more water than a smooth 

 belt or a perfectly smooth and straight rope would do. Some- 

 thing of this kind, perhaps, maybe supposed to t.ake place ; and 

 contrary to the opinion which I at first entertained, above, 

 of the cause of the sensitiveness at low gas-pressures of Barry's 

 sensitive wire-gauze flame, it seems more probable that the 

 flurry and depression of the flame produced by external sou ids 

 is tire result of their action upon the gas-jet below, mixing 

 the gas more thoroughly with air, and giving it explosive 

 properties before it passes through the gauze. The gauze-Hame 

 must be regulated by lowering the gas-jet, until the brink of its 

 stability and tendency to collapse and burn noisily on the gauze 

 is nearly reached, in order to make this destruction of its equili- 

 brium by external noises possible ; and the explanation thus 

 offered of the sensitiveness of the gauze-flame at lower gas-pres- 

 sures than those used with other flames depends upon no assump- 

 tion of mechanical actions of unusual delicacy, or indeed of any 

 peculiar kinds of undulation taking place among the perforatiuns 

 of the gauze. 



I have quite recently seen an instrument connected very 

 closely with the acoustical properties of flames burning on wire- 

 gauze, showing how well instrument-makers have appreciated 

 them, and how actively they are engaged in representing tliem 

 in a convenient form. It resembles Geyer's sounding modifica- 

 tion of Barry's sensitive flame so nearly, that but for its having 

 received no such title from the maker, the source of its original 

 invention might scarcely be considered doubtful ; but it appears 

 more probable, as will be seen from a description in Nature 

 (to be shortly again referred to) by Dr. A. K. Irvine (vol x. p. 273), 

 of Glasgow, ot identically the same instrument patented many 

 years ago for a very different purpose, that the designer of this 

 singing tube may also have been guided by a knowledge of that 

 invention. Even allowing for the general knowledge of the 

 acoustical properties of wire-gauze flames that has for a long time 

 existed, the instrument shows signs of originality of design that 

 cannot easily be accounted for without some such considera- 

 tion. It consists of a brass stand with two sliding brackets, 

 one of which supports, in a split cork, a glass tube tapered 

 above to a point to mix a jet of gas with air. The other arm 

 supports a brass tube five-and-a-half inches high, and about an 

 inch and three-quarters wide, closed at the bottom with a disc of 



gauze held there .ngiiuit a fix-id rim in the tube by a wire ring. 

 The position of the gauze close to the bottom of the tube ami 

 that of the tapering gas-jet under it, as well as the dimensions of 

 the tube, are the counter-part of Mr. Geyer's experiments with 

 Barry's sensitive flame, only diflering in want of adiustibility of 

 the relative positions of the tube and diaphragm of wire-gauze 

 from his arrangement. The arrangement itself is, however, on the 

 other hand, exactly that which Mr. Irvine patented, as will soon be 

 seen, twelve years ago, for use in a new description of miner's 

 safety lamp. The sound produced, when the flame is lighted on 

 the wire-gauze inside the tube and the jet below it is fixed at a 

 proper height, is, as might be anticipated from its high pitch, 

 answering to the short length of the open tube, an excruciatingly 

 piercing note. 



I was not aware that the effect of heat alone in gauze-diaphragms 

 to produce musical sounds in open tubes h«l been observed and 

 investigated, as it is stited to have been by Prof. Barrett, so 

 thoroughly by Prof. Rijke, of Leyden ; and a perusal of that 

 author's description of his experiments, and of his comments upon 

 them, would undoubtedly be of exceeding inteie-t. That the 

 experiment h.is often been repeated since, and has been varied 

 in many ways by those who were acquainted with it, is a conse- 

 quence that I wa? fully prepared to learn, from its great beanty, 

 would follow very speedily upon the first publication of its dis- 

 covery. 



I have never examined sounding and sensitive flames with 

 revolving mirrors ; but the result could scarcely fail to prove 

 very instructive. The indications of his own essays in pursuit of 

 this method contained in Prof. Barrett's letter, both where I have 

 been able to consult the original writings and drawings that he 

 quotes, and where he offers us a short account of further results 

 apparently more noticeable than those obtained before, of the 

 appearance of a particularly active and impressionable sensitive 

 flame alTecled by the vowel sounds, when viewed in a moving 

 mirror, show that the characteristic comportment of these flames 

 is eminently adapted for examination and discussion by such a 

 mode of observation. 



Similar experiments on the chirruping, whistling, trumpeting, 

 and other sounding open flames, obtained by the collision of two 

 jets, examined by Prof. Tyndall and Mr. Cottrell, here suggest 

 themselves ; but I must hasten to bring this long excursive letter 

 to a close. I cannot, however, do so without expressing my 

 obligation to Prof. Barrett for the valuable references and infor- 

 mation that he has been good enough to supply, and for the 

 prompt and ingenuous manner in which he kindly rectified my 

 oblivious association of his name with Mr. Barry's in certain 

 recent observations of the sensitiveness of wire-gauze flames. 

 The notices contained in a short space in his most interesting 

 letter gave me a better acquaintance with the progress of this 

 wide and curious subject, than repeated and anxious inquiries 

 concerning it for several months previously in the scattered pages 

 of many recent scientific journals had enabled me to acquire. 



I must also add my acknowledgments to Mr. T. S. 'Vright 

 and to Mr. A. K. Irvine for the inierestmg notes that they have 

 furnished in Nature (vol. x. p. 273, and p. 286) on the early 

 use of wire-gauze flames to produce vociferously loud sounds in 

 open tu'oes. That large iron tubes specially titled ins'de with 

 gauze-covered (or the so-called " smokeless") gas burners, to 

 produce a mighty sound, should be preserved as working instru- 

 ments of a chemical laboratory in Edinburgh as long ago as the 

 year 1842 ; and that as much as twelve years since a kind of 

 safety-lamp for mines was patented by Mr. Irvine in this and 

 other countries, sounding aloud alarm note when the lamp-flame 

 lights the explosive mixture of fire-damp entering the bottom 

 of the wick-tube through a wire-gauze disc placed there to 

 cover it, are facts that need no comments to show that the sur- 

 passing power of such flames to excite and sustain musical sounds 

 has long been known and used successfully. The excellent cha- . 

 racter and perlormance of the instruments used in 1S42, as 

 described by Mr. Wright, makes it probable that frequent illus- 

 trations of the same kind mast alre.ady have preceded them. On 

 the other hand, from the well-known scitntific eminence of their 

 possessor. Dr. David Boswell Reid, as a skillul director of 

 large works of ventilation, it may also be presumed that they 

 probably presented to his views novelty of some special kind, 

 either of invention or of construction, or of both combined, the 

 result of which was the production of several such superior instru- 

 ments. It may not be impossible from this consideration, at 

 least if no evidence of considerably earlier origin could be pro- 

 duced, to fix the time, and perhaps the authorship by Dr. Reid 

 himself, or by his brother the chemist, Dr. William Reid of 



