PLANT-AUTOGRAPHS—BOSE. 425 
pull exerted by the motile organ is relatively feeble, and in the 
movement of the very small leaflets of Desmodium gyrans or the 
telegraph plant, for instance, a weight so small as four-hundredths 
of a gram is enough to arrest the pulsation of the leaflets. Even 
in the leaf of Mimosa the friction offered is enough to introduce 
serious errors into the amplitude and time relations of the curve. 
This error could not be removed as long as the writer remained in 
continuous contact with the writing surface. I was, however, able 
to overcome this difficulty by making an intermittent, instead of a 
continuous, contact. The possibility of this lay in rendering the 
Fig. 2.—Response curve of primary leaf of Mimosa. The verticallines below the record indicate 
intervals of one minute each. 
writer tremulous. Fresh difficulties arose which were finally elimi- 
nated by an invention depending on the phenomenon of resonance. 
THE RESONANT RECORDER. 
The principle of my resonant recorder depends on a certain phe- 
nomenon, known as resonance or sympathetic vibration. In illus- 
tration of this we may construct an artificial ear tuned to a definite 
note. The drum of the artificial ear is made of thin soap film; a 
beam of light reflected from its surface forms characteristic pattern 
of color on the screen. To various cries this ear remains deaf, but 
the apathy disappears as soon as the note to which the ear is tuned 
is sounded at a distance. On account of sympathetic vibration 
the artificial ear film is thrown into wildest commotion, and the 
hitherto quiescent color pattern on the screen is now converted into a 
whirlpool of indescribably gorgeous color of peacock green and 
molten gold. 
