August Toepler bigraphy, stories - German physicist

August Toepler : biography

September 7, 1836 - March 6, 1912

Toepler electrostatic generator. mercury air pump.]]

August Joseph Ignaz Toepler (7 September 1836 – 6 March 1912) was a German physicist known for his experiments in electrostatics.

Schlieren optical system

Schlieren optics show changes in the condition of a test area of space in the optical path, even when it remains fully transparent. A simplified outline of the arrangement is shown in the scheme at left. A source sends out a beam of light through the apparatus to a film.

Half the field is cut off by a knife-edged screen, K1, which is imaged by a lens, L1, to a position, K1′, in the same plane as a matching screen, K2. The knife-edges of image and screen exactly coincide. A test position, T, is sharply focused on the film. Thus the light flow past K1 to K2 is all cut off from the film if the space at T is completely uniform. Any nonuniformity, such as caused by a wave front in the air at T, causes a scattered light beam to evade the screen, K2 (path a), and reach the film.


Toepler's son Maximilien Toepler was also a physicist, and worked independently in the same field.

Toepler was also famous for inventing the Toepler Pump as seen in the bottom right hand picture.


August Toepler was born on 7 September 1836. He studied chemistry at the Gewerbe-Institut Berlin (1855–1858) and graduated from the University of Jena in 1860. Later Toepler turned to experimental physics. August Toepler was a lecturer of chemistry and physics at the Academy Poppelsdorf (1859-1864). He received a chair of chemistry and chemical technology at the Polytechnic Institute of Riga and he hold this position between 1864 and 1868.

In 1864, he applied Foucault's knife-edge test for telescope mirrors to the analysis of fluid flow and the shock wave. He named this new method schlieren photography, for which he is justifiably famous. He also developed the Toepler machine, an electrostatic influence machine, in 1865 for use in X-ray photography. Improved versions were produced by Wilhelm Holtz, Roger and J. Robert Voss.

In 1868, he became a professor at the University of Graz in Austria, where under his administration a new physical institute has appeared. In 1876, Toepler came to Dresden where he was offered the chair of Experimental Physics. He was a director of the Physical Institute at the Dresden Technical University till his retirement in 1900. His son Maximilian Toepler continued the scientific work independently. Toepler is remembered as an inventor of electrostatic machines, and for his work with air pumps and acoustic waves.

Toepler described also a symmetrical machine (1866) that is a sectorless machine and a similar device is used as a voltage multiplier.

Toepler’s electrostatic machines were made by different people and companies, e.g. a Toepler machine can be found in a Welch Scientific Company (Chicago, USA) catalog. The differences between a Toepler machine, a Holtz machine, and a Toepler-Holtz machine are unclear even in books written when they were vital, modern technology. Sometimes such a machine is called a Holtz-Toepler machine simply because it was made by Holtz, but the original design is still the same as the Toepler machine.

This model of an electrostatic induction generator, very much in vogue for electromedical purposes towards the end of the nineteenth century, is based on the principles of electrophorus and duplicator function. It is derived from the mechanical improvements made between 1865 and 1880 by the physicist August Topler, the German physicist Wilhelm Holtz (1836-1913) and by J. Robert Voss, a mechanician from Berlin. Voss devised this self-excitation model in 1880, perfecting a machine presented by Topler the previous year.

The machine rests upon a footed walnut base. A column horizontally supports the axis of rotation. Two thin, shellacked, parallel glass disks in close proximity one to the other are vertically hinged to this axis. The larger of the two (the rear one), is a fixed disk and rests on the base along the groove of an ebonite insulation disk; the other (the front one), is a smaller mobile disk and rotates by means of a crank that controls a pair of pulleys connected by a cord. On its outer side, the fixed disk carries the inductors, two strips of tinfoil glued in the middle of two, broad paper shields placed diametrically, one beside the other.

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