SENSITIVE FLAMES. 407 



mountain ranges, and other inequalities along the cir- 

 cumference of the earth's disc exposed to the solar action, 

 combined with the rapidity of the earth's motion (diurnal 

 and orbitual) with reference to the sun ; while the 

 weather which such an appearance is held to presage is 

 also accounted for by the atmospheric conditions necessary 

 to enable the phenomenon to take place. 



One of the remarkable discoveries of recent scientific 

 inquiry is that of Mr. Barrett, late Assistant at the Royal 

 Institution, with regard to what are called " sensitive 

 flames." A metal pipe with an orifice of steatite, when 

 emitting such an amount of gas as to afford that quantity 

 of flame which a burner gives forth just before the flame 

 " roars," as we are accustomed to hear it called, from the 

 excessive pressure of the gas, furnishes a light which is 

 exceedingly sensitive to certain sounds. A grave sound 

 such as a low whistle will cause it to shoot out numerous 

 tongues of flame, which subside when the sound is discon- 

 tinued. By different arrangements of the burner this 

 may be varied. An aperture supplying a column of flame 

 of about two feet in length will cower and quiver under 

 the influence of certain sibilant sounds. Words contain- 

 ing the letters, s, x, and z, especially the former, power- 

 fully affect it even when pronounced at a considerable 

 distance from it. And a variety of manifestations may be 

 occasioned by certain notes of the pianoforte. Under one 

 set of conditions the effect being produced by high, and 

 under another by low notes. This peculiarity is mani- 

 festly the effect of vibration on highly-elastic elements, 

 which may either be the gas forming the supporter of 

 combustion, or the metallic orifice from which the flame 

 proceeds. Indeed, every element known is more or less 

 elastic, and it is quite possible to conceive that certain 

 sounds, by the peculiarity of their vibration, could shiver 

 solid bodies to pieces, and that the character of the sound, 



