NATURAL PHILOSOPHY. 183 



Experiments were made upon other liquids besides water, such as mercury 

 and ether. 



Other materials besides liquids were found to afford a similar intensifi- 

 cation of sound from solid bodies, such as lamina? of gutta-percha or of 

 India-rubber and sheets of writing paper, but the amount of augmentation 

 was less. 



The hearing-tubes employed were various. Many of the experiments were 

 performed with the author's ordinary differential stethophone, an instrument 

 described in the Philosophical Magazine for November, 1858. India-rubber 

 tubes fitted with ivory ear-knobs, and with wooden or glass cups (the size 

 of the cup or object-extremity of ordinary stethoscopes), and having an 

 ear-extremity to pass into the meatus, and brass tubes, were also in turn 

 employed. Tubes closed at their distal extremity with solid material, such 

 as glass, did not answer so well as those closed with membrane. 



The water-bag increases the impression conveyed to the ear by the wooden 

 stethoscope, if it be placed between the flat ear-piece and the external ear. 

 It may be employed alone to reinforce sound. The name of Hydrophone has 

 been given to it. 



A postscript is added, in which the author records an experiment made on 

 the bank of the Serpentine river. A sound produced upon the land was 

 heard at a point in the water when it could not be heard at an equal distance 

 on the ground, if the two limbs of the differential stethophone were emplo3 r ed 

 simultaneously. 



The sensation upon the ear, connected by means of a hollow tube with 

 water in sonorous undulations, was found to be much greater than that 

 upon the ear connected with the same water by means of a solid rod. When 

 both tube and solid rod were employed simultaneously, sound was heard 

 in that ear only supplied with the tube. 



ON THE REGISTRATION OF SOUND VIBRATIONS. 



The Abbe Laborde has recently devised the following plan for registering 

 the vibrations of sound. To the ceiling of a room are fixed two rings, some 

 six feet apart, and to these are suspended two wooden rules, about eight 

 feet long. Their lower ends are fastened into a block or wood, which is 

 connected with a pendulum, so that the vibrations may be registered on a 

 piece of glass, the face of which is covered with smoke black. From this 

 photographic impressions may be multiplied, if desirable, to any extent. 

 This apparatus is much less costly than any other hitherto made for regis- 

 tering sounds, and is interesting, since it is an aid toward the invention of 

 machines which shall gradually advance from registering sounds to regis- 

 tering syllables and words. As soon as the wit of man has invented a 

 machine as delicate as the human ear, we can have reporting machines. 

 The idea is certainly far less astonishing than that of the daguerreotype 

 before its invention. If the vibrations of Alight, so much finer than those of 

 sound, are made to register themselves with such wonderful accuracy, why 

 may not the vibrations of sound be made to do the same! 



FIGURES PRODUCED BY SOUND. 



If a drinking glass, or a funnel of about three inches diameter at the edge, 

 be filled with water, alcohol, or ether, and a strong note be made by draw- 



