98 
W. T. BOVIE 
improved instrument, because of the smaller number of checks, requires 
less time for plotting the curves.^ 
The principle of the new instrument will be understood from the 
accompanying figures. Figures I and 2 show the exterior while figure 
3 shows the construction. A and B, fig. 3, is the auxanometer case. 
The plant is attached by a fine wire to the hook C, which is fastened to a 
flat spring. A slight tension on the wire bends this spring downwards. 
As the plant grows the spring moves upwards and touches the screw 
E, thus closing the electrical circuit at D, which up to this time has 
been open, since the other end of the spring and its binding post are 
insulated from the block supporting E. The tension on the spring, 
which is controlled by turning the screw E, is so slight as not to affect 
the rate of growth. 
Through the terminals and i^' the instrument is connected to an 
battery and chronograph. When the contact is made at D, current 
flows through the instrument and the chronograph and the pen of the 
chronograph makes a record. The current through the instrument 
flows from the terminal K to the binding post of the flat spring, along 
the flat spring and on to the screw E. From E it flows through the 
rack F to the pinion wheel G, through a train of gear wheels and their 
supporting framework (not shown in the diagram) to the escapement 
wheel H, then on to the armature J and through the electromagnet / 
to the terminal K\ The electromagnet / is thus energized, and 
attracts the armature /, which is held against H hy d spring. When 
the armature / moves over against the electromagnet it releases the 
pin on the escapement wheel, and at the same time opens the circuit, 
since the contact between H and / is broken. The electromagnet is 
thus deenergized, the armature / returning to its position against the 
escapement wheel H. The escapement wheel is connected with the 
pinion wheel G through a train of gear wheels and the pinion wheel is 
under the tension of a clock spring. Therefore, when the pin on the 
escapement wheel has been released by the movement of the armature 
^ The L. E. Knott Apparatus Company of Boston have developed a special 
chronometer which in addition to making the records, automatically draws a curve 
of the rate of growth. The writer has had no part in the development of this 
chronometer other than to test the experimental model. The instrument does its 
work well, but it has the disadvantage that the record of only one auxanometer 
can be made at one time. With the chronometer which the writer has devised for 
his own use (a drum rotated by an eight-day clock) the record of six auxanometers 
can be made at one time. 
