The accompanying booklet to this Lot begins with some words from a Dr E.E. Slosson, Director of "Science Service", Washington D.C.: "The Dragoyle works to a charm. The only fault I have to find with it is that it is such a fascinating creature that I waste my time watching its manoeuvres when I should be working. Also, it attracts the attention of my visitors and distracts their attention from me, because all they want to know is what it is for and how it works".
Essentially, the instrument works to measure the rate of evaporation in the air by nodding its head backwards and forwards. The booklet advises that "before the Air-tester slows below the minimum value for the room-temperature, you should either introduce the "Air-motion" factor of comfort by means of a draught, artificial or natural, or lower the temperature by letting in cooler air, if this can be done; or do both." There then follows a table relating the range of air-tester head-nods per minute for "correct air comfort for sedentary workers" to temperatures from 60° to 82° Fahrenheit. The example given is of a room at 72°F where the tester moves at 15 strokes per minute. As the table reads that the optimum number of strokes is between 24 and 50, the reader is encouraged in such a situation either to increase air circulation or lower the temperature as required.