Hearing And Seeing Plants Grow

There are several ways of rendering the growth of piants both audible and visible, but tho modus operaiidi in the "latest improved" experiments is as follows: In order to make the growth oí a very vigorous plant visible, a fine platinum wire should be carefulJy attached to the growiug part. The other end of this wire should be attached to a pencil pressing gently against a drum which is boing driven by doek work. If the growth be uniform a straight line is ïnarked on the paper, but tho very slightest increase is shown by inclinad tracing. A slight modifloation of this arrangement renders the growth audible. Iu this experiment the drum must bo coveroii with platiaum fuils of a certain width and separated from each other by spaces of about oue-eighth of au inch. These strips of platintim should be made to complete the circuit of a galvanic battery, to which an electric bell is attached. In this case the bell is kept continnally ringing while the plant is growing the height of the width of the strips used and is silent while the pointer is passing over the spaces between the strips of metal. The growing of corn may be heard direct by means of the microphone, and there are those who declare that they have heard it without any artificial assistauce ever. -