Cylindrical Beetz-type Electroscope (early 1900s)

This is a cylindrical Beetz-type electroscope for qualitative demonstrations of electrostatic phenomena.

Except for the iron base and the insulator, the construction is almost entirely of brass. The two leaves appear to be aluminum. The chamber's interior has been painted black (typical for this type of instrument). This makes the leaves easier to visualize by minimizing any annoying reflections of light inside the chamber. This "paint" might be a conductive Aquadag-like compound. The manufacturer is unknown.

With regard to the usual attribution of this type of electroscope to Beetz, I can only offer the following information.


In 1873, W. Beetz provided the detailed description for a new bifilar electroscope, but the latter was nothing like the cylindrical electroscope shown above. The cylindrical style of electroscope we now attribute to Beetz was described later, in a 1876 paper of his. The paper's title, translated into English, was "On Anomalous Data of the Gold Leaf Electroscope." The following is from an English summary (1876) of Beetz's paper .

"M. Beetz makes an electroscope, in which the case is a horizontal brass tube (12 centimetres diameter and 8 centimetres long) supported on metallic feet. It is closed by vertical glass plates parallel to the plane in which the aluminum leaves diverge. It is very reliable."

The dimensions in the above description are nearly identical to the dimensions of the electroscope featured here, as well as the dimensions of the other Beetz electroscope in the ORAU collection.

It would appear that Beetz designed the cylindrical electroscope so that it would avoid some of the problems associated with glass electroscopes, e.g., a leakage of charge over the glass surfaces.

A device called an electrophorus would normally be used to charge the condenser plate.  For an explanation of how an electroscope can be charged and how an electrophorus works, click here. 

Size: ca. 12" high. The chamber is 4.75" in diameter and 3.5" deep


Anonymous. On Anomalous data of the Gold Leaf Electroscope by M. Beetz. Telegraphic Journal. September 15, 1876.

Beetz, W. Ueber anomale Angaben des Goldbatts-elektroskops. Ann. de Pogg., No. 6, 1876.

Gripon, E. Beetz, W.B. Bifilarelectroscope fur Vorlesungsversuche (Electroscope bifilaire pour les experiences de cours); Carl’s Repertorium, t. IX, p. 18,; 1873. J. Phys. Theor. Appl., 3 (1), pp.67-68. 1874.


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Last updated: 07/25/07
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