649 



III. " On the Intensification of Sound through Solid Bodies 

 by the interposition of Water between them and the distal 

 extremities of Hearing-Tubes." By S. SCOTT ALISON, M.D., 

 Assistant-Physician to the Hospital for Consumption. 

 Communicated by Dr. TYNDALL. lleceived January 20, 



1859. 



(Abstract.) 



In this Paper the author gives an account of various experiments 

 which he has recently made on sounds proceeding through solid 

 bodies. He has found that sounds which are faint, when heard by 

 a hearing-tube applied directly to solid sounding bodies, become 

 augmented when water is interposed between these bodies and the 

 distal extremity of the hearing-tube. He has been able, by the em- 

 ployment of water, to hear the sound of a solid body, such as a 

 table, which, without this medium, has been inaudible. Experi- 

 ments have been made upon water in various amounts and in different 

 conditions. Thus a very thin layer, a mere ring round the edge of 

 the hearing-tube, masses of water in larger or smaller vessels, and a 

 bag of water, have been employed. The results have been the same 

 as regards augmentation. The degree of augmentation was greatest 

 when the hearing-tube was immersed freely in water. In experi- 

 menting upon water in vessels, it was found necessary to close 

 the extremity of the tube to be immersed, by tying over it a piece of 

 bladder or thin india-rubber ; for the entrance of water into the in- 

 terior interfered greatly with the augmentation. 



The effect of water in augmenting sound is materially reduced if 

 even a small amount of solid material be interposed between the 

 water employed and the mouth of the hearing-tube. A piece of 

 wood, not much thicker than a paper-cutter, materially interferes 

 with the augmenting power of water. 



The augmentation of sound thus obtained by water seems to be 

 due to the complete fitting of the liquid on the solid body and also 

 round the mouth of the hearing- tube, whereby the column of air 

 is thoroughly enclosed ; also to the less impediment to the vibrations 

 of the instrument when held in contact with water, than when held 



