of charge captured through induction by the combs is collected by the two mobile, brass collection rings, the terminal spherules of the spark-gap are each charged by the opposite sign with respect to the sign of the comb with which they are in contact. In this manner the machine is able to produce sparks, at times very long ones, especially if the poles of the spark-gap are in contact with the internal shields of the two Leiden jars. Standard direct current was not always available at the turn of the century so that Toepler-Holtz electrostatic generators were used to provide physicians with current for treatment as well as to power the first x-ray devices. They were fairly common and advertised in the Sears catalogue with numerous accessories. This machine built in an oak-and-glass cabinet is a Toepler-Holtz generator made by the Betz company of Chicago ( 1900). It was intended for medical use, and has an X-ray tube controller as an integral part. This machine is of the Toepler-Holtz design and comes from the late 1890s. It was sold to practicing physicians as a potential source for the excitation of X-ray tubes. For this it works quite well, yielding about 1 mA at 80 kV at moderate rates of rotation. Accessories to be found in the drawers are for “electrical treatment” for such things as baldness, lameness, etc. Most are systems of points designed to produce brush discharges. A low table with glass legs is included for electric isolation of the patient. Some of the devices look as though they are instruments of torture even without the application of electricity. The case enclosing the plates should not be opened except for repairs. The machine is operated by turning the crank counterclockwise as one looks at the front. A rotary switch at the center connects or disconnects the Leyden jars to the terminals. The pictured generator is one of the larger types and is made up of 24 glass plates, 6 sets of four each, which were rotated to produce current for therapy. It was made by an unknown maker (Wagner?), 1910. August and Maximilian Toepler started research in the field of gas discharge physics at the Dresden University of Technology. This research particularly resulted in the development of the Schlieren technique. With the application of the “streak method” Toepler succeeded as the first scientist in making acoustic waves in the