196 J. A. POLLOCK. 



From a physical point of view the auricle seems welt 

 adapted for the part which it plays in the detection of small 

 earth movements, both with respect to the extent of the 

 air connected with the ear passage which becomes enclosed 

 when the head rests on the ground, and to its capability 

 of being used as a support for the head. It is, perhaps, not 

 improbable that the exercise of the geophonic function of 

 head and ear, certainly common among primitive people, 

 may have been a factor in the development of the auricle 

 in man. 



A model, which has to a slight extent the appearance, 

 but, when in use, almost exactly the action of the head 

 and ear when detecting earth movements, may be made by 

 embedding a complete ring of rubber tube in a groove in a 

 wooden disc, the ring being about five centimetres in 

 diameter and projecting a couple of millimetres or so below 

 the surface of the wood. A pipe through a hole in the 

 centre of the disc enables the apparatus to be attached by 

 a rubber tube to an ear piece. When placed on the ground 

 the layer of air within the circumference of the ring is 

 enclosed, and the instrument, with an appropriate mass, 

 gives effects not unlike those obtained with the head and 

 ear. 



All appliances of this type, including stethoscopes, have 

 natural periods of vibration, the movements in most cases 

 being only slightly damped. These natural periods give a 

 selective sensitiveness to the instruments, as in all similar 

 cases, and dominant tones to the indications. This matter 

 is of importance when the interpretation of the sounds is 

 in question. I am unable to recognise in my own case a 

 period natural to head and ear 



The Physical Laboratory, 



The University of Sydney. 



