THE STETHOSCOPE. 187 



In carrying out the work fragments of known felspars 

 were used and the composition estimated from a determin- 

 ation of the refractive index corresponded very closely with 

 the known composition. 



Acknowledgements. — The above work was undertaken 

 at the suggestion of Dr. Cotton, and I have to thank him 

 for his assistance in carrying it out. 



The Geological Department, 



The University of Sydney. 



THE STETHOSCOPE, WITH A REFERENCE TO A 

 FUNCTION OF THE AURICLE. 



By J. A. Pollock, d.s c ., f.r.s. 



[Read before the. Royal Society of N. 8. Wales, December 1, 1920.'] 



If apology were needed for a paper on the physics of a 

 simple apparatus in such constant use as the stethoscope, 

 it might well be based, in the first instance, on the remark- 

 able paucity of references to the instrument in physical 

 literature. The name 'stethoscope' does not occur in the 

 subject index 1 to the Royal Society Catalogue of Scientific 

 Papers, 1800 — 1900, nor is the appliance mentioned in any 

 standard work on Sound which I have been able to consult. 

 From medical sources 2 it appears that in discussions on 

 the action of the simpler forms of stethoscope attention 

 has been directed to the 'sound conducting' properties of 

 solid rods and columns of air. As a dynamical aspect of 

 the problem is not mentioned, I am led to consider that 

 the explanation which I have to offer may be new. 



1 Vol. 3, Physics, Part 1. a See, e.g., Williams, B.M.J., Vol. 2, 1907, p. 6. 



