50 



HARDWICKE'S SCIENCE-GOSSIP. 



[Makch 1, 1867. 



often cast aside as soon as brought to light, and 

 contradictions piled up upon no better foundation, 

 are in general the germs of every branch of science ; 

 so the world, wisely perhaps, awards to the master- 

 mind that unravels the tangled web and makes all 

 clear, the full title of an original discoverer. The 

 sounding of a hydrogen flame in a glass tube was 

 first noticed by Dr. Higgins, in 1777. Since then 

 the subject has been investigated by Chladni, De 

 la Rive, Earaday, Wheatstone, Kundt, and others. 

 The action of sounds of a definite pitch on flames 

 inclosed in tubes has been investigated by Count 

 Schaffgotsch and Professor Tyndall. Indeed, under 

 the latter, " The Philosophy of Elame " has for years 

 been one of the leading subjects of investigation in 

 the laboratories of the Royal Institution. The 

 jumping of a fish-tail flame in response to musical 

 sounds was accidentally discovered by Professor 

 Lecomte at a musical party in America. In passing 

 a candle with steadily burning flame rapidly through 

 the air, an indented band of light is produced, and a 

 slightly musical vibration indicates the rhythmic 

 character of the motion. The solution of this 

 problem, and of those which follow, is the subject 

 of Professor Tyndall's lecture, and, as like another 

 Columbus, he has broken the egg, by his aid we 

 shall comprehend another of these ideas which 

 cluster round that comprehensive phrase, "the con- 

 servation of force," as clearly as he has laid before 

 us " heat as a mode of motion." But to proceed : a 

 gas flame having been introduced into a tube 

 sufficiently long and wide, the current of air passing 

 over the flame produces a vibration, which, by the 

 aid of the tube's resonance, becomes a musical 

 sound. Thus, from a tube three feet long the 

 musical note will be rich ; from one six feet long it 

 will be an octave lower ; and in a tube fifteen feet 

 long the deep bass vibrations have an intensity of 

 such power that in the lecture-room, filled by an 

 audience of some six hundred persons, pillars, floors, 

 seats, gallery, and audience are all sensibly shaken. 

 The note rises in pitch as the tube diminishes in 

 length, and the intense heat of the sounding column 

 produces a greater number of vibrations than any 

 organ pipe of the same length. The flame in a tube 

 17f inches long vibrated 459 times in a second, and 

 another in a tube 10f inches long 717 times in a 

 second. These vibrations consist of a series of partial 

 extinctions and revivals of the flame, forming, when 

 viewed in Wheats tone's rotating mirror, a series of 

 flame images of transcendent beauty. 



Other equally interesting experiments served to 

 illustrate the subject : one, which recalled the way 

 in which boys teach jackdaws and jays to speak, by 

 splitting their tongues ; and another, as more plainly 

 showing the cause of the phenomenon, must, how- 

 ever, suffice. The bright flame of a fish-tail, which 

 appeared perfectly insensible to all sounds, musical 

 or not, and to which Handel's Harmonious Black- 



smith would apparently have hammered away to no 

 purpose, was severed in two by a stream of air. 

 This done, no sooner was a whistle sounded than 

 the flame started ; a knock on the table caused the 

 separated flames to re-unite and form for an instant 

 a flame of the ordinary shape. In the second 

 experiment, a steady, clear flame, issuing from a 

 circular orifice, four inches in height, was insen- 

 sible to sound. Baised to ten inches, it responded 

 by a slight quiver to the whistle ; at sixteen inches, 

 the increased quivering showed the flame to be on 

 the brink of roaring, and with a little increase of 

 the pressure it roared, shortening itself at the same 

 time to eight inches ; reducing the pressure, the 

 flame was again extended to sixteen inches. It did 

 not roar, but was on the point of roaring, standing, 

 as it were, on the brink of a precipice, and the 

 whistle then forced it over, upon which it roared, 

 simultaneously shortening itself, as it did before 

 under the increase of pressure. "And herein," says 

 Professor Tyndall, " is the true explanation of all the 

 phenomena of these c sounding or sensitive flames,' 

 that the sonorous pulses furnish the supplement of 

 energy or force necessary to produce the roar and 

 shorten the flame." The pitch of the note chosen to 

 force this flame over the brink of the precipice on 

 which it rests must be equal to the occasion. Eour 

 tuning-forks, vibrating respectively 256, 320, 384, 

 and 512 times in a second, produced no effect on a 

 certain flame. But besides these fundamental notes 

 these forks will sound a series of notes of very high 

 pitch, producing 1,600, 2,000, 2,400, and 3,200 

 vibrations per second ; and to each of these the flame 

 jumped in response, but most energetically in 

 response to the highest note. 



THE SWALLOWS. 



"TNDER this heading appeared in a recent 

 *J number a most interesting letter from E. L. 

 Simmonds, telling us that early in November, 

 1865, when at the mouth of the river Niger, in West 

 Africa, "innumerable swallows passed for a whole 

 day together over his head from seaward, flying in 

 a northerly direction," and he asks, " could they be 

 coming from America ? " Now, as the several 

 habitats of these most interesting birds, and their 

 periodical migrations in the different parts of the 

 world, have engaged my attention for many years 

 past (as indeed the columns of the Field and your 

 own Science Gossip pages will attest), I will con- 

 dense, in as few lines as I can, all the information 

 which I have been enabled to collect from French and 

 English works, regarding the hirundines of Africa. 

 Now these may be classed geographically as four 

 distinct species— according to what I learn from 

 that Ornithological text-book, the Ibis — and those 

 again may be subdivided latitudinally into north 



