242 ANNUAL OF SCIENTIFIC DISCOVERY. 



secondly, that the pulse of arteries beyond the chest takes place in all parts 

 at the same instant, and without any appreciable interval. 



The sphygmoscope forms a good pncuraoscope. It delicately measures 

 the rise and fall of the chest in respiration. It likewise declares the relative 

 duration of inspiration and expiration, and may thus prove useful in the 

 detection of incipient phthisis, and other pulmonary diseases. When the 

 liquid has attained its highest elevation at the end of inspiration, it immedi- 

 ately begins to fall ; but Avhen it has reached the lowest point at the end of 

 expiration it remains there some instants. The ascent is slower than the 

 descent. After the fall of an ordinary expiration, a forced expiration gives a 

 second fall. 



The sphygmoscope (fig. 1,) may be employed without a stand, and is then 

 more portable ; but from the want of a fixed basis, and from the motion of 

 the ribs on which it must rest, its manifestations are less extensive and 

 satisfactory. When employed without a stand, as it must rest upon the ribs, 

 the elastic wall of the chamber should be plain, and not protruding. 



ON THE SOUNDS PRODUCED BY THE COMBUSTION OF GASES 



IN TUBES. 



Professor John Tyndall, in a communication to the London Journal of 

 Gas Lighting, on the above subject, after reviewing the various theories en- 

 tertained at different periods, proceeds to say : In 1818, Mr. Faraday 

 took up the subject, and showed that the tones were produced when the glass 

 tube was enveloped by an atmosphere higher in temperature than 212 Fahr. 

 That they were not duo to aqueous vapor, was further shown by the fact that 

 they could be produced by the combustion of carbonic oxide, lie referred 

 the sounds to successive explosions produced by the periodic combination of 

 the atmospheric oxygen Avith the issuing jet of hydrogen gas. This is un- 

 doubtedly the true source of the sounds. 



I am not aware that the dependence of the pitch of the note on the size of 

 the flame has as yet been noticed. To this point I will, in the first place, 

 briefly direct attention. 



A tube twenty-five inches long was placed over an ignited jet of hydrogen : 

 the sound produced was the fundamental note of the tube. 



A tube twelve and a half inches long Avas brought over the same flame, 

 but no sound was obtained. 



The flame was lowered, so as to make it as small as possible, and the tube 

 last mentioned was again brought over it ; it gave a clear melodious note, 

 which was the octave of that obtained with the twenty-five inch tube. 



The twenty-five inch tube was now brought over the same flame ; it no 

 longer gave its fundamental note, but exactly the same note as that obtained 

 from the tube of half its length. 



Thus we see, that although the speed with which the explosions succeed 

 each other depends upon the length of the tube, the flame has also a voice in 

 the matter : that to produce a musical sound, its size must be such as to 



