Swett & Lewis Type W Tube (1900-1905)

swett tube

The tube shown here was manufactured by the Swett & Lewis Company of Boston Massachusetts. Since Swett & Lewis was purchased by the Electro-Radiation Company in 1906, I am guessing that the tube dates from 1900 to 1905.

Like many Swett & Lewis tubes, it had a somewhat elongate bulb and only employed two electrodes (an cathode and anode). The cup-shaped cathode is located in the slightly expanded portion of the glass arm attached (in the photo) to the left side of the bulb.  As seen in the image to the right, the company name is indicated on the back of the cathode.

The target (anode) is the rectangular sheet of platinum located in the center of the bulb.


According to the company's literature "This ["W"] tube is really a small size D and is intended for static machines, of about six revolving plates, and small coils." The “light anode” made the tube unsuitable for use at higher voltages and currents.

The Swett & Lewis Type S tube is similar, but smaller: about 3" in diameter.

The basic model shown here, without a regulator (adjustment), sold for $6.75. If purchased with a platinum or chemical regulator, it went for $8.75. As a rule, it was considered false economy not to get the regulator.

Size: ca. 13" long and 4" diameter.

Swett & Lewis

Swett & Lewis seemed to prefer elongate tubes. The explanation can be found in one of their catalogs where they noted that an increased distance between the electrical terminals for the anode and cathode minimized the chance that tramp static discharges would occur over the surface of the tube. Such discharges were undesirable because they could puncture the tube.


Swett & Lewis Bulletin No. 33. Coils and X-ray Tubes. Copyright 1903.

X-ray Tubes               Museum Directory

Last updated: 11/07/07
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