Last Issue's "What's That!?!" image:
The answer, taken from the 1903-1904 edition of the Polytechnic Engineer:
"Fig. 8 shows a section of the Electrostatic Laboratory of the Polytechnic Institute of Brooklyn during the progress of a test by the author of this monograph.
The machine upon the left is that manufactured by the Mcintosh Battery and Optical Company, of Chicago, Illinois, and is being driven as a generator by the small direct-current motor seen upon the table on the left. The machine upon the right is that manufactured by the Waite and Bartlett Company of New York and is being driven as a motor by the Mcintosh machine, the connections between
the two machines not being those described under the efficiency tests, the latter connections being an improvement upon those illustrated here, which were heavy insulated wire enclosed in thick glass tubing. Both machines are described below, the Waite and Bartlett machine being No. 3, and the Mcintosh machine No. 4. Upon the table in the rear center is a 15 000-volt Electrostatic Voltmeter.
The machines employed in the experiments upon which this monograph is based were all of the multi-plate type. The first machine, manufactured by the Waite, and Bartlett Company of New York, consists of ten revolving and ten stationary plates, enclosed in an airtight glass case, the air inside being kept dry by a pan of calcium chloride, CaCL. The insulating handles, discharge knobs,
and condenser connections are all on the outside, so that the machine may be operated without opening the case, and consequently this type of machine is but slightly affected by weather conditions.
The machine itself was excited by means of a small Wims-hurst Influence Machine, which was also' enclosed in the case, but which could be rotated by hand from the exterior.
The Holtz Machine proper was rotated by a belt connection between a pulley wheel on its shaft and one on the shaft of a small direct current motor rated at 1000 rev. per min., no volts, and 1.4
h.p. The speed of this motor was regulated by means of an adjustable resistance in its armature circuit. A voltmeter and an ammeter were also introduced into the circuit of the motor armature to
derive the power input.
The second machine, manufactured by the Galvano-Faradic Manufacturing Company of New York, had the same general plan of construction, operation, and regulation as the first, except that it had
only eight revolving and eight stationary plates and was slightly smaller in size.
The third, fourth, and fifth machines, now to be described, were all rotated by a small direct current motor rated at 800 rev. per min., no volts, and 0.25 h.p., the belt connections and the method of regulating the speed of the motor being identical with those of the first two.
The third machine, manufactured by the Waite and Bartlett Company of New York, was exactly like the first machine described, also made by them, except that it had twelve revolving and twelve stationary plates.
The fourth machine, manufactured by the Van Houten and Ten Broeck Company of New York, was similar to the other three, except that its axle was provided with ball bearings, and that there were
twelve revolving and twelve stationary plates.
The fifth machine, manufactured by the Mcintosh Battery and Optical Company of Chicago, Illinois, differs radically from the four previously described, in that it is self-exciting, no auxiliary exciter being required. This type is known as the Toepler Holtz Machine. The excitation is accomplished by means of a pair of generator arms, one on each side of the machine, having brushes and metal clips of brass which hold the stationary plates in place, and also serve to conduct the electricity from the plate to the arm. They are so arranged as to fit over the strips of tin foil leading to the paper sectors pasted on the stationary plate. The brushes make contact only with metal buttons on the revolving plates, not being allowed to make contact with the plate itself. The machine consisted of eight revolving and eight stationary plates.
A sixth machine, manufactured by the Greenpoint Metallic Manufacturing Company of Brooklyn, New York, was the subject of a two-hour test of current and of voltage under varying conditions. Like the Mcintosh machine, this was also a Toepler Holtz, the excitation being accomplished in a precisely similar manner. The machine consisted of sixteen revolving and sixteen stationary plates, but, by means of a mechanical device, four or eight of the revolving plates could be loosened from the axle and prevented from rotating by a brake bearing upon their lower edges. The machine could therefore be converted at will into a twelve-plate or an eight-plate generator. It was operated by belt connection from its axle to the power shaft of the factory, rotating at a constant speed of 265 rev. per min."
