Dr. U. Konio; on Manometric Flames. 



"D 



a greater density, the membrane will of course be driven inwards, 

 and thus expel the gas and cause the flame to rise quickly. If, 

 on the contrary, the air be suddenly rarefied, the membrane 

 becomes drawn outwards, the space within momentarily in- 

 creased, the gas expanded, and the flame lowered. 



A membrane is known to possess, like every other elastic 

 body, only a definite series of notes ; and thus we should suppose 

 that the manometric capsule would only show an effect when 

 the note acting upon it agreed with one of the notes of its 

 membrane. 



But this is not the case ; for besides the vibration which a 

 body makes under the influence of its elasticity, any motion 

 whatever can be forced upon it if only the active force be much 

 greater than the resistance which it can offer. 



For example, let us take a long thin string, tuned to the funda- 

 mental note of 100 vibrations, and place its centre in firm con- 

 nexion with the prong of a strong massive tuning-fork of 110 vi- 

 brations ; it will then clearly move to and fro 110 times in unison 

 with the vibrations of the tuning-fork, although in accordance 

 with its nature it could only execute 100, 200, 300, &c. vibra- 

 tions. In point of fact it does not truly vibrate, but is only 

 mechanically drawn to and fro. 1 This is also the case with the 

 manometric capsule, as it is so constructed that the resistance 

 offered to the condensation and rarefaction of the atmosphere 

 must be considered very trifling, indeed almost nil. One and 

 the same capsule is thus equally effective for every note ; also 

 different capsules, whose membranes have not been tuned in 

 unison, nevertheless give the same results under the influence 

 of the same note. 



If out of several capsules which are fed by the same gas-reser- 

 voir you set one in activity, the flames in all the others are set 

 in motion. Thus, if the membrane be pressed into the capsule, 

 the pressure will not only drive the flame higher from the exit- 

 pipe, but will also spread its influence through the entrance-pipe 

 to the general reservoir, and thence to the other capsules, the 

 flames of which become prolonged, although in a less degree. 

 Of course, a pressure in the contrary direction produces an 

 opposite effect. If, therefore, several capsules are to be em- 

 ployed at the same time, this mutual influence must be annulled. 



I at first sought to attain this end by placing between the re- 

 servoir and the capsules long thin india-rubber tubes; but this 

 did not act quite satisfactorily. 



I attained my object, however, by the use of accessory cap- 

 sules, through which I permitted the gas to pass before I con- 

 ducted it into the manometric capsule ; they are constructed like 

 the others, each consisting of a cavity closed by a thin membrane. 



