on the driving-shaft of an Elbs gravity motor and set in motion.  Electrical connections and interruptions were made by contact with the edge of a platinum slip placed at an inclination to the disc’s tangent, and so as to bear lightly on the passing teeth or surfaces.  The changes in form of a mercury globule, consequent on the adhesion of the liquid to the passing teeth, made it impossible to use the latter medium.  The absolute rate of succession in the series of sounds was controlled by varying the magnitudes of the driving weights and the resistance of the governing fans of the motor.  As the relation of sounds and intervals for any disc was unalterable, a number of such wheels were prepared corresponding to the various numerical groups and temporal sequences examined—­one, for example, having the relations expressed in the musical symbol 3/4 | >q e |*; another having that represented in the symbol 4/4 | >q e e |;* and so on.  Variations in intensity were obtained by mounting a second series of contacts on the same shaft and in alignment with those already described.  The number of these secondary contacts was less than that of the primary connections, their teeth corresponding to every second or third of those.  The connections made by these contacts were with a second loop, which also contained within its circuit the telephone receiver by which the sounds were produced.  The rheostatic resistances introduced into this second circuit were made to depart more or less from that of the first, according as it was desired to introduce a greater or slighter periodic accent into the series.  This mechanism was designed for the purpose of determining the characteristic sequences of long and short elements in the rhythm group.

  Transcriber’s Note: 

The original article showed “3/4 | q q q |” and “4/4 | q q q q |”.  Applying the erratum after the article (below) resulted in fewer beats per measure than indicated by the time signature.  Other possibilities are “3/4 | >q e q. |” and “4/4 | >q e e q q |”.

   “ERRATUM: 

On page 313, line 23, the musical symbols should be a quarter note, accented, followed by an eighth note; in the following line the symbols should be a quarter note, accented, followed by two eighth notes.”

The fourth piece of apparatus consisted essentially of a horizontal steel shaft having rigidly attached to it a series of metallic anvils, fifteen in number, on which, as the shaft revolved, the members of a group of steel hammers could be made to fall in succession from the same or different heights.  The various parts of the mechanism and their connections may be readily understood by reference to the illustration in Plate VIII.  On the right, supported upon two metal standards and resting in doubly pivoted bearings, appears the anvil-bearing shaft.  On a series of shallow grooves cut into this shaft are mounted loose brass collars, two of which are visible on the hither