Abstract
The appliance, as demonstrated, is used with a gasometer in which the bell is suspended by a wire passing over a grooved wheel and continuous with a length of steel measuring-tape, which in turn suspends the counterweight.
The appliance consists of a large and a small grooved wheel mounted on a single axle; from the small wheel a silk thread suspends a double magnet fitted with a hinged iron armature, which, on magnetization, firmly grasps the measuring tape of the gasometer. From the large wheel is suspended a counterweight which outbalances the magnet, permitting the weight to sink to the bottom of its guiding channel.
The tube leading to the gasometer carries an expiratory flutter valve; from the subject's side of this valve, a short take-off leads to a large tambour which operates a riding-arm, making and breaking a current during expiration and inspiration respectively.
At the beginning of expiration, this contract is made a fraction of a second before the gasometer bell begins to move; a relay closes the current which operates the magnet, causing it to firmly grasp the steel tape and ride with it during its full excursion. At the beginning of inspiration, the tambour breaks the circuit, the magnet releases the tape, and the counterweight drops to its original position. The counterweight carries a pen which records its movements on a revolving drum.
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