. Electronic apparatus for biological research . Insulation Fixed capacitor plate Phosphor-bronze diaphragm (moving capacitor plate) Pressure applied here Figure Hansen capacitance manometer some very sophisticated examples of the use of electrical equivalent circuits in the solution of mechanical problems. Investigation of the vibration sensitivity of spiders In an attempt to discover how a spider detects the presence of its prey on the web, Dr. D. A. Parry has carried out some preliminary experiments on vibrations of the web, using transducers designed and constructed by J. A. Popple*.
. Electronic apparatus for biological research . Insulation Fixed capacitor plate Phosphor-bronze diaphragm (moving capacitor plate) Pressure applied here Figure Hansen capacitance manometer some very sophisticated examples of the use of electrical equivalent circuits in the solution of mechanical problems. Investigation of the vibration sensitivity of spiders In an attempt to discover how a spider detects the presence of its prey on the web, Dr. D. A. Parry has carried out some preliminary experiments on vibrations of the web, using transducers designed and constructed by J. A. Popple*. These experiments illustrate well some of the difficulties encountered in the application of transducers to biological material; they also illustrate how a simple transducer, designed specifically for the one purpose, may lead to results otherwise obtainable only with delicate and complex apparatus. The first experiments sought to measure the vibrations induced in a web by a fly caught on it. A very small and light differential transformer of the type shown in Figure was used. The armature, which was brought into contact with the web, was a mumetal wire about 0-1 mm diameter and 5 mm long, flexibly mounted through a sheet of rubber 0-05 mm thick. For easy recording of vibration frequencies up to 1,000 c/s an energizing frequency of 10 kc/s was used, with the output of the transducer feeding the Y plates of an oscillograph. A moving-film camera gave a record in * I am indebted to Dr. Parry and Mr. Popple for allowing me to describe this preliminary (and unpublished) work, particularly as both successful and unsuccessful applications of transducers are mentioned. 506
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