THE FRANKLIN INSTITUTE
[J. F. I. seated lady. However, a memberof the staff submitted the writings and drawings, seven in number, to a very careful scrutiny, with the result that what had formerly been regarded as decorative detail on one drawing proved to be the statement, written in French, that the drawing was "done by Maillardet's automaton." It was known that Maillardet's writer and draughtsman had passed through the handsof several well known showmen in the nineteenth century. It had last been reported as being in the Peiping Museum. However, further research here and in Switzerland has served to prove that The Franklin Institute automaton is Maillardet's masterpiece.
The principal part of any writing or drawing mechanism is that which initiates and controls the movements of the hand. The other bodily movements that contribute to realism can be simulated without much difficulty, for they need not be accurate. But the motions of writing or drawing must be very closely controlled if the work produced is to be readable or understandable.
It is also necessary that the control be carried out in three dimensions. since the machine must make a two-dimensional drawing and also lift the pen off the paper, Thus three directional components must be provided to move the writing arm of the automaton.
By far the most convenient method of satisfying these requirements is to use a set of three metal disc cams, which Maillardet adopted. The arm joints have the same play as those of the human arm, except that the wrist does not bend. There were no electric motors available when Maillardet built his automaton 150 years ago, but he constructed spring motors to operate his mechanism smoothly. The "brain" of the automaton is three groups of cams. Two groups produce horizontal and vertical motion on the drawing, while the third group takes the pen on and off the paper. Each disc in a group has a mate in each of the other groups with which it operates simultaneously. Indexing the cams is done by a large drum fitted with a single helical rib. The drum is rotated by the spring motor, and on its end are engraved the titles of the seven drawings and verses, so that the operator can set the drum for any desired drawing. Each drawing requires several sets of cams for its execution, and at the end of each revolution the cams stop with the followers resting on transverse bars. They remain undisturbed as the indexing drum automatically slides the next set of cams into alignment, so that the work can continue. The time spent in this operation is utilized to advantage, for the doll raises her pen, straightens up, and looks critically at the paper, as if deciding what to draw or write next.
"The Jaquet-Droz automata in the Neuchatel Museum in Switzerland do not possess such an extensive repertoire as does the Maillardet automaton but their work is more delicate. However, the very delicacy of the work does not permit frequency of operation. In order to witness them in operation, the visitor must time his visitto the Museum for a Sunday. The Maillardet writer and draughtsman operates cheerfully every day and produces an average of 10,000 drawings and verses during the course of the year.